The Study of Nebular Emission on Nearby Spiral Galaxies in the IFU

Hindawi Publishing CorporationAdvances in AstronomyVolume 2013 Article ID 627867 14 pageshttpdxdoiorg1011552013627867

Review ArticleThe Study of Nebular Emission on Nearby SpiralGalaxies in the IFU Era

Fernando Fabiaacuten Rosales-Ortega

Instituto Nacional de Astrofısica Optica y Electronica Luis E Erro 1 72840 Tonantzintla PUE Mexico

Correspondence should be addressed to Fernando Fabian Rosales-Ortega frosalesinaoepmx

Received 7 August 2013 Accepted 27 September 2013

Academic Editor Jose Manuel Vılchez Medina

Copyright copy 2013 Fernando Fabian Rosales-Ortega This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

A new generation of wide-field emission-line surveys based on integral field units (IFU) is allowing us to obtain spatially resolvedinformation of the gas-phase emission in nearby late-type galaxies based on large samples of HII regions and full two-dimensionalcoverage These observations are allowing us to discover and characterise abundance differentials between galactic substructuresand new scaling relations with global physical properties Here I review some highlights of our current studies employing thistechnique (1) the case study of NGC 628 the largest galaxy ever sampled with an IFU (2) a statistical approach to the abundancegradients of spiral galaxies which indicates a universal radial gradient for oxygen abundance and (3) the discovery of a new scalingrelation of HII regions in spiral galaxies the local mass-metallicity relation of star-forming galaxies The observational propertiesand constrains found in local galaxies using this new technique will allow us to interpret the gas-phase abundance of analoguehigh-z systems

1 Introduction

The study of the interstellar medium (ISM) like many otherareas of astrophysics has undergone a remarkable accelera-tion in the flow of data over the last few years Large surveyssuch as the 2dFGRS [1] SDSS [2] GEMS [3] or COSMOS [4]to name a few have revolutionised our understanding of theUniverse and its constituents as they have enabled us to studythe global properties of a large number of objects allowingfor meaningful statistical analysis to be performed togetherwith a broad coverage of galaxy subtypes and environmentalconditions

The nebular emission arising from extragalactic objectshas played an important role in this new understandingNebular emission lines have been historically the main toolat our disposal for the direct measurement of the gas-phaseabundance at discrete spatial positions in low redshift galax-iesThey trace the youngmassive star component in galaxiesilluminating and ionizing cubic kiloparsec-sized volumes ofISM Metals are a fundamental parameter for cooling mech-anisms in the intergalactic and interstellar medium star-formation stellar physics and planet formation Measuring

the chemical abundance in individual galaxies and galacticsubstructures over a wide range of redshifts is a crucial stepto understanding the chemical evolution and nucleosynthesisat different epochs since the heavy atomic nuclei tracethe evolution of past and current stellar generations Thisevolution is dictated by a complex array of parametersincluding the local initial gas composition star-formationhistory (SFH) gas infall and outflows radial transport andmixing of gas within discs stellar yields and the initialmass function Although it is difficult to disentangle theeffects of the various contributors determinations of currentelemental abundance constrain the possible evolutionaryhistories of the existing stars and galaxies and the interactionof galaxies with the intergalactic medium The details ofsuch a complex mechanism are still observationally notwell established and theoretically not well developed andthreaten our understanding of galaxy evolution from the earlyUniverse to the present day

The relevance of the study of the ISM in the local Universecannot be underestimated since it actually constitutes thebases of the methods and calibrations employed to derive

2 Advances in Astronomy

abundance and their relations with global galaxy parame-ters in high redshift galaxies (eg [5 6]) objects that aretypically solely identifiable by their emission line spectraNearby galaxies offer a unique opportunity to study theSFH-ISM coupling on a spatially resolved basis over largedynamic ranges in gas density and pressure metallicity dustcontent and other physically relevant parameters of gas anddust However most of the observations targeting nebularemission in nearby galaxies have beenmadewithmultibroad-band and narrow-band imaging in the optical and near-infrared or single-aperture or long-slit spectrographs result-ing in samples of typically a dozen or fewer HII regionsper galaxy These observations have been used to derivethe properties of their dominant stellar populations gascontent and kinematics (eg [7ndash9]) Nevertheless despitemany efforts it has been difficult to obtain a complete pictureof the main properties of these galaxies especially those onesthat can only be revealed by spectroscopic studies (like thenature of the ionization andor the metal content of the gas)This is because previous spectroscopic studies only sampleda very few discrete regions in these complex targets (eg[10 11]) or used narrow-band imaging of specific fields toobtain information of star-forming regions and the ionizedgas (eg [9]) and in many cases they were sampling veryparticular types of regions [12ndash15] Integrated spectra overlarge apertures were required to derive these properties ina more complete way (eg drift-scanning [16]) but even inthese cases only a single integrated spectrum is derived andthe spatial information is lost

On the other hand although large spectroscopic surveyslike the 2dFGRS or the SDSS do provide a large numberof objects sampled and vast statistical information they aregenerally limited to one spectrum per galaxy thus missingall the radial information and spatially resolved propertiesof the galaxy These surveys have been successful to describethe integrated properties and relations of a large number ofgalaxies along a wide redshift range But galaxies are complexsystems not fully represented by a single spectrum or justbroad band colours Disc and spheroidal components arestructurally and dynamically different entities with differentSFH and chemical evolution A main drawback of this tech-nique is that it leads to aperture bias that is difficult to controlas the area covered to integrate the spectra corresponds todifferent physical scales at different redshifts (eg SDSS)and also the physical mechanisms involved in ionizing thegas may be very different within the sampled area as thiswould include regions with emission due to diffuse ionizedgas (DIG) shocks or AGNLINER activity

The advent of Multi-Object Spectrometers (MOS) andIntegral Field Spectroscopy (IFS) instruments with largefields of view (FoV) now offers us the opportunity toundertake a new generation of surveys based on a full two-dimensional (2D) coverage of the optical extent of nearbygalaxies The first application of IFS to obtain spatiallyresolved continuously sampled spectroscopy of certain por-tions of nearby galaxies was due to the SAURON project[17 18] SAURON was specifically designed to study thekinematics and stellar populations of a sample of nearbyelliptical and lenticular galaxiesThe application of SAURON

to spiral galaxies was restricted to the study of spiral bulges[19] However IFS was rarely used in a ldquosurvey moderdquo toinvestigate sizeable samples There were several reasons forthe lack of a systematic study targeting galaxies in the localUniverse using IFS that could cover a substantial fraction oftheir optical sizes The reasons included small wavelengthcoverage fibre-optic calibration problems but mainly thelimited FoV of the instruments available worldwide MostIFUs have a FoV of the order of arcsec preventing a goodcoverage of the target galaxies on the sky in a reasonabletime even with a mosaicking technique Furthermore insome cases the emission lines used in chemical abundancestudies were not covered by the restrictedwavelenght range ofthe instruments Moreover the complex data reduction andvisualisation imposed a further obstacle

In order to fill this gap in the last few years we starteda major observational programme aimed at studying the2D properties of the ionized gas and HII regions in arepresentative sample of nearby face-on spiral galaxies usingIFS The spatially resolved information provided by theseobservations is allowing us to test and extend the previousbody of results from small-sample studies while at the sametime it opens up a new frontier of studying the 2D gasabundance on discs and the intrinsic dispersion inmetallicityprogressing from a one-dimensional study (radial abundancegradients) to a 2D understanding (distributions) allowing usat the same time to strengthen the diagnostic methods thatare used to measure HII region abundance in galaxies

Here we present the highlights of our current studiesemploying this large spectroscopic database (1) the case ofNGC628 the largest galaxy ever sampledwith IFS (2) an IFS-based statistical approach to the abundance gradients of spiralgalaxies and (3) the discovery of a new scaling relation of HIIregions in spiral galaxies and how we use it to to reproducemdashwith remarkable agreementmdashthe mass-metallicity relation ofstar-forming galaxies

2 A IFS Sample of Nearby Disc Galaxies

The studies here described were performed using IFS dataof a sample of nearby disc galaxies The observations weredesigned to obtain continuous coverage spectra of the wholesurface of the galaxies They include observations from thePPAK IFSNearby Galaxies Survey PINGS [20] and a sampleof face-on spiral galaxies fromMarmol-Queralto et al [21] aspart of the feasibility studies for the CALIFA survey [22 23]a legacy project which aims to observe a statistically completesample of sim600 galaxies in the local Universe all projects arecarried out at the Centro Astronomico Hispano-Aleman ofCalar Alto Spain

PINGS represented the first attempt to obtain continuouscoverage spectra of the whole surface of a representativesample of late-type galaxies in the nearby Universe Thisfirst sample includes normal lopsided interacting and barredspirals with a good range of galactic properties and star-forming environments with available multiwavelength publicdata (eg see Figure 1)The second sample consists of visuallyclassified face-on spirals from Marmol-Queralto et al [21]

Advances in Astronomy 3

NGC 1637

NGC 628

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Figure 1 (a) Examples of the PINGS IFS mosaics each panel shows a 119861-band Digital Sky Survey image of the galaxy with the PPAK mosaicpointings as overlaid hexagons indicating the FoV of the central fibre bundle (b) Examples of the face-on spirals drawn from the Marmol-Queralto et al [21] sample of IFS galaxies each panel shows a colour-composite SDSS image of the galaxy with the PPAK FoV footprintoverlaid

extracted from the SDSS DR4 imaging sample selectinggalaxies brighter than r lt 1575mag with redshifts in therange 0005 lt 119911 lt 0025 (selection in volume and limitingmagnitude) and from face-on disc galaxies included in theDiskMass Survey [24] with appropriate sizes to fill the FoV ofthe PPAK instrument (angular isophotal-diameter selectionsee below)

Both samples were observed with the PMAS spectro-graph [25] in the PPAK mode [26 27] on the 35m telescopein Calar Alto with similar setup resolutions and integrationtimes covering their optical extension up to sim24 effectiveradii within a wavelength range sim3700ndash7000 A The PPAKfiber bundle consists of 382 fibers of 27 arcsec diameter eachOf these 382 fibers 331 (the science fibers) are concentratedin a single hexagonal bundle covering a field-of-view of 74 times64 arcsec2 with a filling factor of sim60 The sky backgroundis sampled by 36 additional fibers distributed in 6 bundles of6 fibers each along a circle sim72 arcsec from the center of theinstrument FoV

In the case of PINGS the observations consisted of IFUspectroscopic mosaics for 17 spiral galaxies within a maxi-mum distance of 100Mpc the average distance of the sampleis 28Mpc (for 119867

0= 73 km sminus1Mpcminus1) Most of the objects

in PINGS could not be covered in a single pointing withIFS instruments so a new observing-reduction techniquehad to be developed to perform accurate mosaicking of thetargets The spectroscopic mosaicking was acquired duringa period of three years and the final data set comprisesmore than 50 000 individual spectra covering in total an

observed area of nearly 80 arcmin2 and an observed surfacewithout precedents by a IFS study up to that point (the casestudy of NGC 628 presented in Section 3 is based in thedata of this survey) For the second sample the galaxieswere observed over fifteen nights in several observing runsThe main difference is that for the latter sample a singlepointing strategy using a dithering scheme was appliedwhile for the largest galaxies of the PINGS survey a mosaiccomprising different pointingswas requiredThis is due to thedifferences in projected size considering the different redshiftrange of both samples the PINGS galaxies correspond to119911 sim 0001ndash0003 while for the face-on spirals it is 119911 sim001ndash0025Therefore in both survey samples the data extentcorresponds to about sim2 effective radii for all galaxies (Theeffective radius is classically defined as the radius at whichone half of the total light of the system is emitted) So the finalsample comprises 38 objects with a redshift range betweensim0001 and 0025 Although this sample is by no means astatistical subset of the galaxies in the local Universe it is arepresentative sample of face-on mostly quiescent and spiralgalaxies at the considered redshift range (see Figure 1)

Data reduction was performed using R3D [31] obtainingas an output a data cube for each galaxy with a final spatialsampling between 1-2 arcsecpixel which translates to a linearphysical size between a few hundreds of parsecs to sim1 kpcUsing this database we catalogued more than asymp2500 HIIregions with good spectroscopic quality in all 38 galaxiesrepresenting one of the largest and more homogeneous2D spectroscopic HII region surveys ever accomplished


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Figure 2 (a) Spatial map of the fibres within the IFS mosaic of NGC 628 where nebular emission was detected Blue fibres indicate regionsabove a SN threshold for a proper abundance analysis and grey fibres correspond to a diffuse emission The size and position of the fibres(at real scale) are displayed in the standard NE-positive orientation The crosshairs mark the central reference point of the IFS mosaic Thecolour intensity of each fibre in the blue sample has been scaled to the flux intensity of H120572 for that particular spectrum (b) Oxygen abundancemap of NGC 628 derived by applying the O3N2 calibrator [28] to the emission line maps of the galaxy The figure shows a clear gradient inmetallicity with more abundant regions in the inner part or the galaxy Figure adapted from Sanchez et al [29] and Rosales-Ortega et al [30]

The discussion presented in Sections 4 and 5 is based on thesedatabases The primary scientific objectives of these surveyswere to use the 2D IFS observations to study the small andintermediate scale variation in the line emission and stellarcontinuum by means of pixel-resolved maps across the discsof nearby galaxies as described in the following sections

3 NGC 628 A Case Study of IFS-BasedNebular Emission Studies

NGC 628 (or M 74) is the largest galaxy in projected angularsize (sim105 times 95 arcmin2 119911 sim 000219 sim 9Mpc) of thePINGS sample Due to the large size of NGC 628 comparedto the FoV of the PPAK instrument (72 times 64 arcsec2) amosaicking scheme was adopted employing 34 differentpointings The initial pointing was centered on the bulge ofthe galaxy Consecutive pointings followed a concentric ring-shaped pattern adjusted to the shape of the PPAKbundle (seeFigure 1)The observations of this galaxy spanned a period ofthree years The area covered by all the observed positionsaccounts approximately for 34 arcmin2 making this galaxythe widest spectroscopic survey ever made on a single nearbygalaxy The spectroscopic mosaic contains 11094 individualspectra

With such dimensions this galaxy allows us to study the2Dmetallicity structure of the disc the second order proper-ties of its abundance distribution andmdashas a very important

byproductmdasha complete 2D picture of the underlying stellarpopulations of the galaxy Note that the linear physical scalethat a single PPAK fibre samples at the assumed distanceof the galaxy is sim120 pc This scale can be compared to thephysical diameter of a well-known HII region in our Galaxythat is the Orion nebula (119863 sim 8 pc) or to the extent of whatis considered prototypes of extragalactic giant HII regionssuch as 30 Doradus (119863 sim 200 pc) or NGC 604 (119863 sim 460 pc)The area sampled by an individual fibre in the mosaic wouldsubtend a fraction of a typical giant HII region in NGC 628but the same area would fully encompass a number of smalland medium size HII regions of the galaxy (see Figure 2)

The IFS analysis of NGC 628 was taken as a case studyin order to explore different spectra extraction and analysismethodologies taking into account the signal-to-noise of thedata the 2D spatial coverage the physical meaning of thederived results and the final number of analysed spectraTheanalysis performed on this object represents an example ofthe potential and extent of studies based on IFS on nearbygalaxies In the first paper of the series ([29] hereafterPaper I) we present a study of the line emission and stellarcontinuum of NGC 628 by means of pixel-resolved mapsacross the disc of the galaxy This study includes a qualitativedescription of the 2D distribution of the physical propertiesinferred from the line intensity maps and a comparison ofthese properties with both the integrated spectrum of thegalaxy and the spatially resolved spectra In the second article([30] hereafter Paper II) we present a detailed spatially


resolved spectroscopic abundance analysis based ondifferentspectral samples extracted from the area covered by the IFSobservations of NGC 628 and we define a spectra selec-tion methodology specially conceived for the study of thenebular emission in IFU-based spectroscopic observationsThis allows us to derive the gas chemistry distribution acrossthe surface of the galaxy with unprecedented detail In thethird paper of the series (Sanchez-Blazquez et al submittedhereafter Paper III) we present a stellar population analysis ofthe galaxy after applying spectral inversionmethods to derive2-dimensional maps of star-formation histories and chemicalenrichment

In Paper I spatially resolved maps of the emission lineintensities and physical properties were derived for NGC 628Contrary to previous attempts to perform a 2D wide-fieldanalysis based on narrow-band (or Fabry-Perot) imagingwhich only allowed a basic analysis of the physical parametersandor required assumptions on the line ratios includedwithin individual filters (eg H120572) the emission line mapspresented in this paper were constructed from individual(deblended) emission lines at any discrete spatial locationof the galaxy where enough signal-to-noise was found Thisfact allowed investigating the point-to-point variation of thephysical properties over a considerable area on the galaxyExtinction ionization and metallicity-sensitive indicatormaps were derived from reddening corrected emission linemaps In general they show that the ionized gas in thesespiral galaxies exhibits a complex structure morphologicallyassociated with the star-forming regions located along thespiral arms The (thermal) ionization is stronger along thespiral arms associatedwith theHII regions andmore intensein the outer than in the inner ones Indeed the surface SFRis an order of magnitude stronger in the outer HII regions atdistance larger than sim100 arcsec (45 kpc) than in the innerones Considering that in these outer regions there is a lowermass density the growing rate of stellar mass is considerablylarger there than in the inner ones Therefore the growth ofthe galaxy is dominated by the inside-out process

The spatially resolved distribution of the abundanceshows a clear gradient of higher oxygen metallicity valuesfrom the inner part to the outer part of the galaxy andalong the spiral arms (see right-panel of Figure 2) Howeverin some instances the value of the oxygen abundance (andother physical properties like extinction and the ionizationparameter) varies withinwhat would be considered a classicalwell-definedHII region (orHII complex) showing some levelof structure Indeed the 2D character of the data allows us tostudy the small-scale variation of the spectra within a givenemitting areaThe values of the emission line ratiosmeasuredusing different extraction apertures vary considerably as afunction of the aperture size and the scatter of the centralvalue is larger than the statistical error in the measurementsreflecting that this might in fact be a physical effect Byconstructing 2Dmaps of the oxygen abundance distributionswe found that the 2Dmetallicity structure of the galaxy variesdepending on the metallicity calibrator employed in orderto derive the oxygen abundance Different calibrators findregions of enhanced log(OH) at spatial positions which arenot coincident among them This implies that the use of

different empirical calibrations does not only reflect in a lin-ear scale offset but may introduce spurious inhomogeneitiesThis information is usually lost in a simple radial abundancegradient and that might be relevant when constructing achemical evolution model based on a particular abundancedetermination (see Figure 3)

The emission line maps presented in Paper I proved to beuseful in describing the general 2D properties of the galaxyMore robust conclusions were presented in Paper II wherewe analysed specific individual regions across the disc of thegalaxy either by taking individual spectra above as a certainSN threshold or by coadding spectra with the same physicalproperties and comparing the results in the 2D context Withthe firstmethodwewere able to identify regions of interstellardiffuse emission (see left panel of Figure 3) while with thesecond we created a classic catalogue of HII regions froma purely geometrical principle that is by coadding fibresconsidered to belong to the same morphological region

Some highlights of this study (which also apply to the restof the PINGS galaxies analysed so far) are the following

(1) Despite the large number of spectra contained in theoriginal observed mosaic the final number of fibrescontaining analysable spectra of enough signal-to-noise for a spectroscopic study of the ionized gasrepresents only a reduced percentage of the totalnumber of fibres contained in the full IFS mosaicFor the particular case of NGC 628 less than 10of the total area sampled by the IFU observations isconsidered of sufficient quality

(2) Independently of the abundance calibrator used themetallicity distribution of NGC 628 is consistent witha nearly flat distribution in the innermost regions ofthe galaxy (120588120588

25lt 02) a steep negative gradient for

02 ≲ 120588120588

25lt 1 and a shallow or nearly constant

distribution beyond the optical edge of the galaxythat is implying a multimodality of the abundancegradient of NGC 628 The same feature is observedfor theNO versus120588 distributionThe existence of thisfeature may be related to the differences in the 2D gassurface density and star-formation rate between theinner and outer disc which inhibits the formation ofmassive stars in the outer regions causing a lack ofchemical evolution in the outer disc compared withthe inner regions

(3) The observed dispersion in the metallicity at a givenradius is neither a function of spatial position nor dueto low SN of the spectra and shows no systematicdependence on the ionization conditions of the gasimplying that the dispersion is real and is reflecting atrue spatial physical variation of the oxygen content(see Figure 3)

(4) The values of the oxygen abundance derived fromthe integrated spectrum for each calibrator equalthe abundance derived from the radial gradient ata radius 120588 sim 04120588

25 confirming for this galaxy

the previous results obtained for other objects thatis that the integrated abundance of a normal disc


0 5 10 15 20 25

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Figure 3 (a) Radial abundance gradient derived for NGC 628 based on the PINGS HII region catalogue (green symbols) and HII regionsfrom the literature (black symbols) using the O3N2 calibrator The horizontal grey lines correspond to the abundance derived using theintegrated spectrum as reported in Paper I The top119883-axis values correspond to the projected radii in arcsec for the radial average data Notethe flattening of the gradient for innermost regions of the galaxy and for radii gt 120588

25 that is a multimodality of the abundance gradient (b) 2D

distribution of the oxygen abundance derived from the IFS H II regions catalogue of NGC 628 (plus selected HII regions from the literature)for the KK04 (top-left) metallicity calibrators The shape and colours of the symbols correspond to the difference Δ [12 + log(OH)] equiv Δlog(OH) between the abundance obtained on each HII region with respect to the characteristic abundance 12 + log(OH)

120588=0412058825of the same

calibrator grouped into bins of 00 plusmn01 02 dex (eg +01 dex = 005 le Δlog (OH) lt 015) The large symbol in red colour stands for thelocation of theHII regionwith themaximum amount of 12 + log(OH)measured for that calibratorThe grey thick lines define the operationalspiral arms of the galaxy The dotted circle corresponds to the size of the optical radius 120588

25 Figure adapted from Rosales-Ortega et al [30]

galaxy correlates with the characteristic gas-phaseabundance measured at 120588 sim 04120588

25

(5) While trying to find axisymmetric variations of themetallicity content in the galaxy we found slightvariations between the central oxygen abundanceand slopes for both the geometrical (quadrants) andmorphological (arms) regions of the galaxy How-ever these small variations fall within the expectederrors involved in strong-line empirical calibrations(see Figure 4) If the radial trends in the ionizationparameter andmetallicity abundance were somewhatdistinct this would indicate that to a certain extentthe physical conditions and the star-formation his-tory of different-symmetric regions of the galaxywould have evolved in a different manner Likewise[32] found no evidence for significant large-scaleazimuthal variations of the oxygen abundance acrossthe whole disk of M 101 and marginal evidence forthe existence of moderate deviations from chemicalabundance homogeneity in the interstellarmediumofthis galaxy

In the case of the stellar populations in Paper III wederive maps of the mean (luminosity and mass weighted)age and metallicity that reveal a negative age gradient andthe presence of structures such as a nuclear ring previously

seen in molecular gas (see Figure 5) The disc is dominatedin mass by an old stellar component at all radii sampled bythe IFS data while the percentage of young stars increaseswith radius as predicted in an inside-out formation scenariowhere outer parts of the disc formed later due to theincreasing timescales for gas infall with radiusWe also detectan inversion of the metallicity gradient at the very centre ofthe galaxy (sim1 kpc) where apparently there exists a ring ofold stars at this distance with a trend to younger ones at thevery center Similar results are found in theMilkyWay (MW)using Open Clusters and Cepheids that is a clear bimodalgradient for the older population with a flat outer plateauand a more continuous gradient for the younger population(eg [33ndash36]) This behaviour has also been reported inother galaxies mostly SaS0 where the inner regions of theirbulges present bluer colors consistent with younger stellarpopulations (eg [37])

The relevance of this study regarding the nebular emis-sion is that the young component shows ametallicity gradientthat is very similar to that of the gas and that is flatterthan that of the old stars Although the metallicity gradientsfor the young stars and the gas also show a break this ismuch less prominent than for the old stars The position ofthe break is more coincident with the corotation radius ofthe oval distortion than that of the spiral pattern which is


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North spiral armSouth spiral arm

Radius 12058812058825lo

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(b)

Figure 4 (a) BPT diagnostic diagram for HII regions coded according to the geometric position (quadrants) with respect to the an arbitraryaxis drawn across the galaxy surface The locus of different sectors does not show a clear trend or do not populate a clearly visible region onany diagram compared to the rest of the quadrants Points from all the regions are equally distributed within the cloud of points on eachdiagnostic diagram indicating that the emission line ratios of the HII regions are not a function of azimuthal angle across the disc (b) Radialgradients of the ionization parameter log 119906 for morphologically selected HII regions of NGC 628The panel shows the log 119906 versus 120588 relationfor the regions belonging to the north and south spiral arms of the galaxy The difference between the two spiral arms resides in the slope ofthe gradient of log 119906 for the north arm and the values of log 119906 increase moderately with galactocentric distance while for the south armthe ionization parameter increases with a steeper slope although within the errors of the linear fittings Figure adapted from Rosales-Ortegaet al [30]

beyond the radius sampled by our data We speculate aboutthe possible origen of this break the possibilities being dueto star-formation variation with the spiral pattern speed orthat is due to radial mixing produced by either the spiralarms the oval distortion or a coupling of both We arguethat NGC 628 could represent a good example of secularevolution due to the presence of a dissolving bar In thisscenario the strong bar has funneled large amounts of gasinto the central regions while radial flows induced in the dischave flattened the OH gradient Nuclear starbursts resultingfrom the gas sinking into the center contributed to the bulgersquosgrowth until enough mass was accreted to dissolve the bar bydynamical instabilities The oval distortion observed in thecentral region could be the remains of the bar Forthcomingstudies analysing a sample of galaxies with different massesand showing different morphological features (eg bars ofdifferent strength spiral arms with different morphologiesetc) using for example the CALIFA survey that will helpto elucidate the importance of the different mechanismsproducing radial mixing in the galaxy discs

4 Hints of a Universal Abundance Gradient

IFS offers the possibility to analyse and study a single objectin great detail such as the case of NGC 628 described

above However it also offers the unique chance of studyingthe spectroscopic properties of thousands of HII regionsin a homogeneous way We used our catalogue of HIIregions introduced in Section 2 to characterize the radialtrends and the physical properties of the HII regions ofthe galaxy sample However contrary to the case of NGC628 where the HII regions on the disc of the galaxy werebasically selected and extracted by-hand the HII regionsin these galaxies were detected spatially segregated andspectrally extracted using HIIexplorer [39] a new automaticprocedure to detect HII regions based on the contrastof the H120572 intensity maps extracted from the data cubesOnce detected the algorithm provides with the integratedspectra of each individual segmented region This change ofparadigm is totally necessary when working with thousandsof HII regions contrary to the case of a handful of targetsin classic long-slit spectroscopy We detected a total of 2573HII regions with good spectroscopic quality This is by farthe largest spatially resolved nearby spectroscopic HII regionsurvey ever accomplishedThe emission lines were decoupledfrom the underlying stellar population using FIT3D [40]following a robust and well-tested methodology [20 29]Extinction-corrected flux intensities of the stronger emissionlines were obtained and used to select only star-formingregions based on typical BPT diagnostic diagrams The final


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Mass-weighted log(age (year)) steckmap

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Figure 5 Mean age 2-D maps weighted by the mass (a) and by the light (b) of the stars The different regions correspond to a Voronoi-tessellation binning scheme performed to the IFS mosaic of NGC 628 Figure adapted from Sanchez-Blazquez et al (submitted)

sample comprises 1896 high-quality spatially resolved HIIregionsaggregations of disc galaxies in the local Universe[39]

It is well known that different spectroscopic propertiesof HII regions show strong variations across the area of discgalaxies In particular some of these parameters (eg oxygenabundance EW[H120572] etc) show a strong radial gradientthat in average indicates that more evolved metal rich stellarpopulations are located in the center of galaxies and lessevolved metal poor ones are in the outer ones Despitethe several different studies describing these observationalevents there is a large degree of discrepancy between theactual derived parameters describing the gradients (i) slopeof the gradient (ii) average value and dispersion of the zero-point and (iii) scale length of the truncation In general thisismostly due to different observational biases and the lack of aproper statistical number of analysed HII regions per galaxy

For each galaxy of our sample we derived the correlationcoefficient the slope and the zero point of a linear regressionfor a number of parameters showing radial distributionsacross the discs of the galaxies For those properties showinga strong correlation we investigated if the gradient wasuniversal within our range of explored parameters Wefound that for the equivalent width of H120572 and the oxygenabundance the slopes of the gradients are consistent with aGaussian distribution that is the dispersion of values foundfor each individual galaxy is compatible with the average onenot showing strong statistical deviationsThis implies that wecan define a characteristic value for the slope and that we donot find a population of galaxies with slopes inconsistent with

this normal distribution The right panel of Figure 6 showsthe radial density distribution for the oxygen abundancederived using the O3N2 indicator [28] once scaled to theaverage value at the effective radius for each galaxyThe radialdistance was normalised to the effective radius of each galaxyThe solid line shows the average linear regression found foreach individual galaxy The red-dashed line shows the actualregression found for all the HII regions detected for all thegalaxies

Our results seem to indicate that there is a universalradial gradient for oxygen abundance and the equivalentwidth of H120572 when normalized with the effective radii ofthe galaxies that is they present a radial gradient thatstatistically has the same slope for all the galaxies in oursample The derived slopes for each galaxy are compatiblewith a Gaussian random distribution and are independent ofthe morphology of the analysed galaxies (barrednonbarredgrand-designflocculent) This is one of the most importantresults in the abundance gradients of spiral galaxies obtainedthanks to the use of IFS

5 The Local Mass-Metallicity Relation

The existence of a strong correlation between stellar massand gas-phase metallicity in galaxies is a well-known factThe mass-metallicity (M-Z) relation is consistent with moremassive galaxies being more metal-enriched after the sem-inal work on this relationship by Lequeux et al [41] it wasfirmly established observationally by Tremonti et al ([42]hereafter T04) using the SDSS However there has been no


+lo

g(O

H)

9

88

86

84

0 05 1 15 2

minus084

minus021

040

103

log(

O3N

2)Average abundance of solar neighborhood at Rsun

Linear fit to all HII regions minus011 dexRe

Average linear fit (all galaxies) minus012 dexRe

Mean value at radial bins sim015Re

RRe

Figure 6 Radial oxygen abundance density distribution for thewhole HII region spectroscopic sample discussed in the text Thefirst contour indicates the mean density with a regular spacing offour times this value for each consecutive contour The light-bluesolid circles indicate the mean value (plus 1 minus 120590 errors) for eachconsecutive radial bin of sim 015 119877

119890 The average error of the derived

oxygen abundance is shown by a single error bar located at the top-right side of the panelThe solid-orange square indicates the averageabundance of the solar neighbourhood at the distance of the Sunto the Milky-Way galactic center The lines represent linear fits toall galaxies (black) and all HII regions (dotted red) independentlyshowing a universal slope simminus01 dex119877

119890 Figure is adapted from

Rosales-Ortega et al [38]

major effort to test the M-Z relation using spatially resolvedinformation We used our IFS observations in order to testthe distribution of mass and metals within the discs of thegalaxies We derived the (luminosity) surface mass density(ΣLum 119872⊙ pc

minus2) within the area encompassed by our IFS-segmented HII regions using the prescriptions given by Belland de Jong [43] to convert 119861-119881 colors into a 119861-band mass-to-light ratio (119872119871)

The left panel of Figure 7 shows the striking correlationbetween the local surface mass density and gas metallicityfor our sample of nearby HII regions that is the local M-Z relation extending over sim3 orders of magnitude in ΣLumand a factor sim8 inmetallicity [38]The notable similarity withthe global M-Z relation can be visually recognised with theaid of the blue lines which stand for the [42] fit (plusmn02 dex)to the global M-Z relation shifted arbitrarily both in massand metallicity to coincide with the peak of the HII regionM-Z distribution Other abundance calibrations were testedobtaining the same shape (and similar fit) of the relation

In addition we find the existence of a more general rela-tion between mass surface density metallicity and the equiv-alent width of H120572 defined as the emission-line luminositynormalized to the adjacent continuum flux that is a measureof the SFR per unit luminosity [44] This functional relationis evident in a 3D space with orthogonal coordinate axesdefined by these parameters consistent with |EW(H120572)| being

inversely proportional to both ΣLum andmetallicity as shownin Figure 8 As discussed in Rosales-Ortega et al [38] weinterpret the localM-Z-EW(H120572) relation as the combinationof (i) the well-known relationships between both the massand metallicity with respect to the differential distributionsof these parameters found in typical disc galaxies that isthe inside-out growth and (ii) the fact that more massiveregions form stars faster (ie at higher SFRs) thus earlier incosmological times

In order to test whether the globalM-Z relation observedby [42] using SDSS data is a reflection (aperture effect) of thelocal HII region mass-density versus metallicity relation weperform the following exercise We simulate a galaxy withtypical 119872

119861and 119861-119881 values drawn from flat distributions

in magnitude (minus15 to minus23) and colour (sim04minus1) A redshiftis assumed for the mock galaxy drawn from a Gaussiandistribution with mean sim01 and 120590 = 005 with a redshiftcut 002 lt 119911 lt 03 in order to resemble the SDSS [42]distribution The mass of the galaxy is derived using theintegrated 119861-band magnitudes 119861-119881 colours and the average119872119871 ratio following Bell and de Jong [43] The metallicityof the mock galaxy is derived using the local M-Z relationwithin an aperture equal to the SDSS fiber (3 arcsec) that isthemetallicity that corresponds to themass density surface atthis radiusThe process is repeated over 10000 times in orderto obtain a reliable distribution in the mass and metallicity ofthe mock galaxies

The right panel of Figure 8 shows the result of thesimulation that is the distribution of the mock galaxies intheM-Z parameter space We reproducemdashwith a remarkableagreementmdashthe overall shape of the global M-Z relationassuming a local M-Z relation and considering the apertureeffect of the SDSS fiber The overlaid lines correspond tothe [42] fit (black) and the Kewley and Ellison [45] plusmn02 dexrelation (blue) for which the agreement is extremely goodover a wide range of masses The result is remarkableconsidering that we are able to reproduce the global M-Zrelation over a huge dynamical range using a local M-Zrelation derived from a galaxy sample with a restricted rangein mass (92 lt log119872Lum lt 112) and metallicity (83 lt 12 +log(OH) lt 89) indicated by the rectangle shown in the rightpanel of Figure 8

Therefore by using the power of IFS applied to a sampleof nearby galaxies we demonstrate the existence of a localrelation between the surface mass density gas-phase oxygenabundance and |EW(H120572)| in sim2000 spatially resolved HIIregions of the Local Universe The projection of this distri-bution in the metallicity versus ΣLum planemdashthe local M-Z relationmdashshows a tight correlation expanding over a widerange in this parameter space We use the localM-Z relationto reproduce the global M-Z relation by means of a simplesimulation which considers the aperture effects of the SDSSfiber at different redshifts

Note that the ldquolocalrdquo M-Z-|EW(H120572)| relation is concep-tually different from the ldquoglobalrdquoM-Z-SFR relation proposedby Lara-Lopez et al ([46] dubbed FP) Mannucci et al ([47]dubbed FMR) or Hunt et al [48] based on the integratedspectra of galaxies (the basic difference between these rela-tions is the proposed shape in the 3D distribution that is a


90

85

12+

log(

OH

) [O

3N2]

1 10 100 1000ΣLum (M⊙ pcminus2)

(a)

90

85

12+

log(

OH

) [O

3N2]

1 10

NGC 1058UGC 9965UGC 3091

100 1000

log|

EW(H120572)|

ΣLum (M⊙ pcminus2)

(b)

Figure 7 (a) The relation between surface mass density and gas-phase oxygen metallicity for sim2000 HII regions in nearby galaxies the localM-Z relationThe first contour stands for the mean density value with a regular spacing of four time this value for each consecutive contourThe blue circles represent the mean (plus 1120590 error bars) in bins of 015 dex The red dashed-dotted line is a polynomial fit to the data Theblue lines correspond to the [42] relation (plusmn02 dex) scaled to the relevant units Typical errors for ΣLum and metallicity are represented (b)Distribution of HII regions along the localM-Z relation for three galaxies of the sample at different redshiftsThe size of the symbols is linkedto the value of |EW(H120572)| being inversely proportional to ΣLum and metallicity as shown Figure is adapted from Rosales-Ortega et al [38]

12+

log(

OH

)

90

88

86

84

82

0000 0505

1010

15

15

20

20

25

25 30 35 log|EW

(120572)|

(A)

log(ΣLum ) (M⊙ pcminus2)

(a)

12+

log(

OH

)

9

85

8

75

Tremonti et al (2004) [42]Kewley et al (2008) [45]

107 108 109 1010 1011 1012

MLum (M⊙)

(b)

Figure 8 (a) 3D representation of the local M-Z-EW(H120572) relation The size and color scaling of the data points are linked to the valueof logΣLum (ie low-blue to high-red values) The projection of the data over any pair of axes reduces to the local M-Z M-EW(H120572) andmetallicity-EW(H120572) relations An online 3D animated version is available at httptinyurlcomlocal-mass-metallicity (b) Distribution ofsimulated galaxies in the M-Z plane assuming a local M-Z relation and considering the aperture effect of the SDSS fiber as explained inthe text The contours correspond to the density of points while the circles represent the mean value (plus 1120590 error bars) in bins of 015 dexThe black line stands for the [42] fitting while the blue lines correspond to the Kewley and Ellison [45] plusmn02 dex relation The rectangleencompasses the range in mass and metallicity of the galaxy sample Figure is adapted from Rosales-Ortega et al [38]

surface or a plane) However the obvious parallelism betweenthese two scaling relations deserves a discussion While theldquolocalrdquo M-Z-|EW(H120572)| relation is related to the intrinsicphysics involved in the growth of the galaxy disc in an inside-out scenario the existence of the ldquoglobalrdquoM-Z-SFR relation isexplained according to Mannucci et al [47] by the interplay

of infall of pristine gas and outflow of enriched material atdifferent redshifts epochs supporting the smooth accretionscenario where galaxy growth is dominated by continuousaccretion of cold gas in the local Universe However Sanchezet al [49] using CALIFA data found no secondary relationof the mass and metallicity with the SFR other than the one


induced by the primary relation of this quantity with thestellar mass The same was found with respect to the specificSFR rate The results by Sanchez et al [49] agree with ascenario in which gas recycling in galaxies both locally andglobally is much faster than other typical timescales suchlike that of gas accretion by inflow andor metal loss due tooutflows In essence late-typedisc-dominated galaxies seemto be in a quasi-steady situation with a behavior similar tothe one expected from an instantaneous recyclingclosed-boxmodel

In this scenario the inner regions of the galaxy form firstand faster increasing the gas metallicity of the surround-ing interstellar medium As the galaxy evolves and growswith time the star-formation progresses radially creating aradial metallicity gradients in the disk of spirals Mass isprogressively accumulated at the inner regions of the galaxyraising the surface mass density and creating a bulge withcorresponding high metallicity values but low SSFR (low|EW(H120572)|) that is an ldquoinside-outrdquo galaxy disk growth Insuch a case the local M-Z relation would reflect a morefundamental relation between mass metallicity and star-formation efficiency as a function of radius equivalent toa local downsizing effect similar to the one observed inindividual galaxies Following this reasoning the origin of theglobalM-Z relation can be explained as the combined effectof the existence of the localM-Z relation an aperture bias dueto the different fibers covering factors of the spectroscopicsurveys fromwhich the FMRandFPwere derived (as second-order effect) and a possible selection of a bias of the galaxypopulations which are most common at a particular redshiftand may not reflect the physics of how galaxies evolveSupporting evidence in favour of the inside-out scenario ofgalaxy growth comes from the recent analysis of the spatiallyresolved history of the stellar mass assembly in galaxies of thelocal Universe [50] In summary the existence of the M-Z-SFR relation could also be interpreted as a scaled-up versionof the local M-Z-sSFR relation in the distribution of star-forming regions across the discs of galaxies as described inRosales-Ortega et al [38] and confirmed by Sanchez et al[49] that is the relationship is not primary but obtainedfrom the sum of a number of local linear relations (and theirdeviations) with respect to the galaxy radius

6 Conclusions

The emergence of a new generation of instrumentation thatis multiobject and integral field spectrometers with largefields of view capable of performing emission-line surveysbased on samples of hundreds of spectra in a 2D contextare revolutionising themethods and techniques used to studythe gas-phase component of star-forming galaxies in thenearby Universe (objects which were typically studied withsmall samples based on long-slit spectroscopy) A new bodyof results is coming out from these studies opening upa new frontier of studying the 2D structure and intrinsicdispersion of the physical and chemical properties of the discsof nearby spiral galaxies In this paper we review some ofthe projects that in the last years tackled for the first time

the problem of obtaining spatially resolved spectroscopicinformation of the gas in nearby galaxies PINGS representedthe first endeavour to obtain full 2D coverage of the discsof a sample of spiral galaxies in the nearby Universe ThePINGS sample covered different galaxy types includingnormal lopsided interacting and barred spirals with a goodrange of galactic properties and star-forming environmentswith multiwavelength public data The spectroscopic dataset comprises more than 50 000 individual spectra coveringan observed area of nearly 80 arcmin2 an observed surfacewithout precedents by an IFS study by the time

The IFS analysis of NGC 628 the largest spectroscopicmosaic on a single galaxy was taken as an example of thenewmethodology and analysis that could be performed witha large spectroscopic database for a single object The con-tribution of PINGS also resides in defining a self-consistentmethodology in terms of observation data reduction andanalysis for present and future IFS surveys of the kind aswell as a whole new set of visualization and analysis softwarethat has been made public to the community (eg [51 52])Despite all the complexities involved in the observationsdata reduction and analysis PINGS proved to be feasibleIn less than a three-year period it was possible to builda comprehensive sample of galaxies with a good range ofgalactic properties and available multiwavelength ancillarydatamaximising both the original science goals of the projectand the possible archival value of the survey In fact thescience case of the PINGS project was the inspiration for theongoing CALIFA survey The face-on spirals from Marmol-Queralto et al [21] were part of the feasibility studies forthe CALIFA survey On completion CALIFA will be thelargest and the most comprehensive wide-field IFU surveyof galaxies carried out to date It will thus provide aninvaluable bridge between large single aperture surveys andmore detailed studies of individual galaxies

61 Results fromOther IFU Projects on Star-Forming GalaxiesOther projects have followed this initiative for example theMitchell spectrograph instrument at McDonald Observatory(aka VIRUS-P) is currently used to carry out two small IFSsurveys namely VENGA [53] and VIXENS [54] VENGA(VIRUS-P Exploration of Nearby Galaxies) is an integralfield spectroscopic survey which maps the disks of 30nearby spiral galaxies in a very similar manner to PINGSin terms of spectral coverage resolution and area sampled(3600 Andash6800 A sim5 A FWHM sim07R

25) although with a

different spatial resolution (56 arcsec FWHM) Their targetsspan a wide range in Hubble type star-formation activitymorphology and inclination Likewise PINGS the VENGAgroup used the data cubes of their observations to produce2D maps of the star-formation rate dust extinction electrondensity stellar population parameters the kinematics andchemical abundance of both stars and ionized gas and otherphysical quantities derived from the fitting of the stellarspectrum and the measurement of nebular emission linesTheir first results focus on (1) the spatially resolved star-formation law of NGC 5194 where they give support to theevidence for a low and close to constant star-formation


efficiency (SFE = 120591minus1) in the molecular component of theinterstellar medium [55] and (2) using IFS observations ofNGC 628 they measure the radial profile of the 12CO(1ndash0) to H

2conversion factor (119883C119874) in this galaxy and study

how changes in119883C119874 follow changes inmetallicity gas densityand ionization parameter [56] and also they use the IFSdata to propose a new method to measure the inclination ofnearly face-on systems based on the matching of the stellarand gas rotation curves using asymmetric drift corrections[53] In the case of VIXENS (VIRUS-P Investigation of theeXtreme ENvironments of Starburst) their goal of our surveyis to investigate the relation between star-formation and gascontent in the extreme environments of interacting galaxypairs and mergers on spatially resolved scales of 02ndash08 kpcby using IFS of 15 interactingstarburst galaxies VIXENSwill make extensive use of multiwavelength data in order toinvestigate the star-formation in this object including datafrom Spitzer GALEX IRAM CARMA archival CO and Himaps These projects and datasets are clearly focused on spe-cific science questions adopting correspondingly optimizedsample selection criteria and also observing strategies

Other surveys in the local Universe using the powerof IFS for a detailed study of nearby galaxies include thenext generation surveys like Sydney university AAO MOSIFU [57] (SAMI) and Mapping Nearby Galaxies at APOPI Kevin Bundy IPMU (MaNGA) or the new generationinstrumentation for Very Large Telescope (VLT ESO) likeMulti Unit Spectroscopic Explorer [58] (MUSE) which aimat studying the the chemical and dynamical evolution historyand dark matter contents of galaxies the physical role ofenvironment in galaxy evolution when where and why doesstar-formation occur and so forth based on spatially resolvedspectroscopic surveys of 104ndash105 galaxies The continuouscoverage spectra provided by the imaging spectroscopytechnique employed in these projects are already allowingus to study the small and intermediate linear scale variationin line emission and the gas chemistry for a statisticallyrepresentative number of galaxies of the nearbyUniverseTheprimary motivation common to all of these observationalefforts is to use this information to link the properties ofhigh redshift galaxies with those we see around us todayand thereby understand the physical processes at play inthe formation and evolution of galaxies The power andimportance of all these projects resides in the fact that theywill provide an observational anchor of the spatially resolvedproperties of the galaxies in the local Universe which willhave a potential impact in the interpretation of observedproperties at high redshift from new generation facilitiessuch as the James Webb Space Telescope (JWST) the GiantMagellanTelescope (GMT) or the EuropeanExtremely LargeTelescope (E-ELT) projects that will hopefully revolutionisethe understanding of our Universe in future years

Acknowledgments

Based on observations collected at the Centro AstronomicoHispano-Aleman (CAHA) at Calar Alto operated jointly bythe Max-Planck Institut fur Astronomie and the Instituto de

Astrofısica de Andalucıa (CSIC) Fernando Fabian Rosales-Ortega acknowledges the Mexican National Council forScience and Technology (CONACYT) for financial supportunder the Programme Estancias Posdoctorales y Sabaticas alExtranjero para laConsolidacion deGrupos de Investigacion2010ndash2012 The author also acknowledges financial supportfor the ESTALLIDOS collaboration by the SpanishMinisteriode Ciencia e Innovacion under Grant AYA2010-21887-C04-03

References

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[2] D G York J Adelman J E Anderson et al et al ldquoThesloan digital sky survey technical summaryrdquoThe AstronomicalJournal vol 120 no 3 article 1579 2000

[3] H-W Rix M Barden S V W Beckwith et al ldquoGEMS galaxyevolution frommorphologies and SEDsrdquo Astrophysical Journalvol 152 no 2 pp 163ndash173 2004

[4] N Scoville H Aussel M Brusa et al ldquoThe cosmic evolutionsurvey (COSMOS) overviewrdquo Astrophysical Journal Supple-ment Series vol 172 no 1 pp 1ndash8 2007

[5] T Nagao R Maiolino and A Marconi ldquoGas metallicity diag-nostics in star-forming galaxiesrdquo Astronomy and Astrophysicsvol 459 no 1 pp 85ndash101 2006

[6] R Maiolino T Nagao A Grazian et al ldquoAMAZE I Theevolution of the mass metallicity relation at z gt 3rdquo Astronomyand Astrophysics vol 488 no 2 pp 463ndash479 2008

[7] R C Kennicutt and P W Hodge ldquoH II regions in NGC 628III H-alpha luminosities and the luminosity functionrdquo TheAstrophysical Journal vol 241 article 573 1980

[8] J Belley and J-R Roy ldquoThe abundance gradients across thespiral galaxies NGC 628 and NGC 6946rdquo Astrophysical Journalvol 78 no 1 pp 61ndash85 1992

[9] P A Scowen J J Hester J S Gallagher EWilcots andTW IdtldquoHSTWFPC-2 observations of typical star formation in M101rdquoin Proceedings of the 189th AASMeeting vol 28 p 1360 Bulletinof the American Astronomical Society 1996

[10] J R Roy and J-RWalsh ldquoImaging spectroscopy of H II regionsin the barred Spiral galaxy NGCrdquo Monthly Notices of the RoyalAstronomical Society vol 234 article 977 1988

[11] R C Kennicutt Jr and D R Garnett ldquoThe compositiongradient in M101 revisited I H II region spectra and excitationpropertiesrdquo Astrophysical Journal Letters vol 456 no 2 pp504ndash518 1996

[12] M L McCall P M Rybski and G A Shields ldquoThe chemistryof galaxies I the nature of giant extragalactic HII regionsrdquoTheAstrophysical Journal vol 57 no 1 1985

[13] L Van Zee J J Salzer M P Haynes A A OrsquoDonoghueand T J Balonek ldquoSpectroscopy of outlying HII regions inspiral galaxies abundances and radial gradientsrdquo AstronomicalJournal vol 116 no 6 pp 2805ndash2833 1998

[14] M Castellanos A I Dıaz and E Terlevich ldquoA comprehensivestudy of reported high-metallicity giant HII regions I detailedabundance analysisrdquoMonthly Notices of the Royal AstronomicalSociety vol 329 no 2 pp 315ndash335 2002

[15] M Castellanos A I Dıaz and G Tenorio-Tagle ldquoOn thelarge escape of ionizing radiation from giant extragalactic HII


regionsrdquo Astrophysical Journal Letters vol 565 no 2 pp L79ndashL82 2002

[16] JMoustakas andR C Kennicutt Jr ldquoAn integrated spectropho-tometric survey of nearby star-forming galaxiesrdquo AstrophysicalJournal vol 164 no 1 pp 81ndash98 2006

[17] R Bacon Y Copin G Monnet et al ldquoThe SAURON project Ithe panoramic integral-field spectrographrdquo Monthly Notices ofthe Royal Astronomical Society vol 326 no 1 pp 23ndash35 2001

[18] P T de Zeeuw M Bureau E Emsellem et al ldquoThe SAURONproject II sample and early resultsrdquo Monthly Notices of theRoyal Astronomical Society vol 329 no 3 pp 513ndash530 2002

[19] K Ganda J Falcon-Barroso R F Peletier et al ldquoLate-typegalaxies observed with SAURON two-dimensional stellar andemission-line kinematics of 18 spiralsrdquo Monthly Notices of theRoyal Astronomical Society vol 367 no 1 pp 46ndash78 2006

[20] F F Rosales-Ortega R C Kennicutt S F Sanchez et alldquoPINGS the PPAK IFS nearby galaxies surveyrdquoMonthly Noticesof the Royal Astronomical Society vol 405 pp 735ndash758 2010

[21] EMarmol-Queralto S FMarmol R AMarino et al ldquoIntegralfield spectroscopy of a sample of nearby galaxies I sampleobservations and data reductionrdquo Astronomy and Astrophysicsvol 534 article A8 2011

[22] S F Sanchez R C Kennicutt AGil de Paz et al et al ldquoCALIFAthe calar alto legacy integral field area surveyrdquo Astronomy andAstrophysics vol 538 article 8 2012

[23] B Husemann K Jahnke S F Sanchez et al et al ldquoCALIFAthe calar alto legacy integral field area surveyrdquo Astronomy ampAstrophysics vol 549 article 87 25 pages 2013

[24] M A Bershady M A W Verheijen R A Swaters D RAndersen K B Westfall and T Martinsson ldquoThe diskmasssurvey I overviewrdquo Astrophysical Journal Letters vol 716 no1 pp 198ndash233 2010

[25] M M Roth A Kelz T Fechner et al ldquoPMAS the Potsdammulti-aperture spectrophotometer I design manufacture andperformancerdquo Publications of the Astronomical Society of thePacific vol 117 no 832 pp 620ndash642 2005

[26] M A W Verheijen M A Bershady D R Andersen et al ldquoTheDisk Mass project science case for a new PMAS IFU modulerdquoAstronomische Nachrichten vol 325 no 2 pp 151ndash154 2004

[27] A Kelz M A W Verheijen M M Roth et al ldquoPMASthe potsdam multi-aperture spectrophotometer II the wideintegral field unit PPakrdquo Publications of the Astronomical Societyof the Pacific vol 118 no 839 pp 129ndash145 2006

[28] M Pettini and B E J Pagel ldquo[O III][N II] as an abundanceindicator at high redshiftrdquo Monthly Notices of the Royal Astro-nomical Society vol 348 no 3 pp L59ndashL63 2004

[29] S F Sanchez F F Rosales-Ortega R C Kennicutt et al ldquoPPAKWide-field integral field spectroscopy of NGC 628 I the largestspectroscopic mosaic on a single galaxyrdquoMonthly Notices of theRoyal Astronomical Society vol 410 no 1 pp 313ndash340 2011

[30] F F Rosales-Ortega A I Dıaz R C Kennicutt and SF Sanchez ldquoPPAK wide-field integral field spectroscopy ofNGC628 II emission line abundance analysisrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 3 pp 2439ndash24742011

[31] S F Sanchez ldquoTechniques for reducing fiber-fed andintegral-field spectroscopy data an implementation onR3Drdquo Astronomische Nachrichten vol 327 p 850 2006

[32] Y Li F Bresolin and R C J Kennicutt ldquoTesting for azimuthalabundance gradients in M101rdquo The Astrophysical Journal vol766 article 17 2013

[33] Andrievsky S M Bersier D Kovtyukh et al ldquoUsing Cepheidsto determine the galactic abundance gradient II towards thegalactic centerrdquo Astronomy and Astrophysics vol 384 pp 140ndash144 2002

[34] S Pedicelli G Bono B Lemasle et al ldquoOn the metallicitygradient of the Galactic diskrdquo Astronomy and Astrophysics vol504 no 1 pp 81ndash86 2009

[35] J R D Lepine P Cruz J Scarano et al ldquoOverlappingabundance gradients and azimuthal gradients related to thespiral structure of the Galaxyrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 1 pp 698ndash708 2011

[36] B Lemasle P Francois K Genovali et al et al ldquoGalacticabundance gradients from Cepheids alpha and heavy elementsin the outer diskrdquo In Press httpxxxtauacilabs13083249

[37] J-M Deharveng R Jedrzejewski P Crane M J Disney andB Rocca-Volmerange ldquoBlue stars in the center of the S0 galaxyNGC 5102rdquoAstronomy andAstrophysics vol 326 no 2 pp 528ndash536 1997

[38] F F Rosales-Ortega S F Sanchez J Iglesias-Paramo et alldquoA new scaling relation for HII regions in spiral galaxiesunveiling the true nature of the mass-metallicity relationrdquo TheAstrophysical Journal vol 756 article L31 2012

[39] S F Sanchez F F Rosales-Ortega R A Marino et al et alldquoIntegral field spectroscopy of a sample of nearby galaxiesrdquoAstronomy and Astrophysics vol 546 article A2 2012

[40] S F Sanchez N Cardiel M A W Verheijen S Pedrazand G Covone ldquoMorphologies and stellar populations ofgalaxies in the core of Abell 2218rdquoMonthly Notices of the RoyalAstronomical Society vol 376 no 1 pp 125ndash150 2007

[41] J Lequeux M Peimbert J F Rayo A Serrano and S Torres-Peimbert ldquoChemical composition and evolution of irregularand blue compact galaxiesrdquoAstronomy andAstrophysics vol 80pp 155ndash166 1979

[42] C A Tremonti T M Heckman G Kauffmann et al ldquoThe ori-gin of the mass-metallicity relation insights from 53000 star-forming galaxies in the sloan digital sky surveyrdquo AstrophysicalJournal Letters vol 613 no 2 pp 898ndash913 2004

[43] E F Bell and R S de Jong ldquoStellar mass-to-light ratios and theTully-Fisher relationrdquoAstrophysical Journal Letters vol 550 no1 pp 212ndash229 2001

[44] R C Kennicutt ldquoStar formation in galaxies along the Hubblesequencerdquo ARA Stronomy and Astrophysics vol 36 article 1891998

[45] L J Kewley and S L Ellison ldquoMetallicity calibrations and themass-metallicity relation for star-forming galaxiesrdquo Astrophysi-cal Journal Letters vol 681 no 2 pp 1183ndash1204 2008

[46] M A Lara-Lopez J Cepa A Bongiovanni et al ldquoA funda-mental plane for field star-forming galaxiesrdquo Astronomy andAstrophysics vol 521 no 2 article L53 2010

[47] F Mannucci G Cresci R Maiolino A Marconi and AGnerucci ldquoA fundamental relation between mass star forma-tion rate and metallicity in local and high-redshift galaxiesrdquoMonthly Notices of the Royal Astronomical Society vol 408 no4 pp 2115ndash2127 2010

[48] L Hunt L Magrini D Galli et al et al ldquoScaling relations ofmetallicity stellar mass and star formation rate in metal-poorstarbursts I a fundamental planerdquoMonthly Notices of the RoyalAstronomical Society vol 427 no 2 pp 906ndash918 2012

[49] S F Sanchez F F Rosales-Ortega B Jungwiert et al et alldquoMass-metallicity relation explored with CALIFArdquo Astronomyand Astrophysics vol 554 article 58 2013


[50] E Perez R Cid Fernandes R M Gonzalez Delgado et al et alldquoThe evolution of galaxies resolved in space and time an inside-out growth view from the CALIFA surveyrdquo The AstrophysicalJournal Letters vol 764 no 1 2013

[51] F F Rosales-Ortega ldquoPINGSoft an IDL visualisation andmanipulation tool for integral field spectroscopic datardquo NewAstronomy vol 16 pp 220ndash228 2011

[52] F F Rosales-Ortega S Arribas and L Colina ldquoIntegratedspectra extraction based on signal-to-noise optimization usingintegral field spectroscopyrdquo Astronomy and Astrophysics vol539 article A73 2012

[53] G A Blanc T Weinzirl M Song et al et al ldquoThe virus-P exploration of nearby galaxies (venga) survey design dataprocessing and spectral analysis methodsrdquo The AstronomicalJournal vol 145 article 138 2013

[54] A L Heiderman N J I Evans K Gebhardt et al ldquoTheVIRUS-P Investigation of the extreme environments of starbursts(VIXENS) survey and first resultsrdquo in Proceedings of the FrankN Bash Symposium on New Horizons in Astronomy 2011

[55] G A Blanc A Heiderman K Gebhardt N J Evans andJ Adams ldquoThe spatially resolved star formation law fromintegral field spectroscopy virus-p observations of NGC 5194rdquoAstrophysical Journal Letters vol 704 no 1 pp 842ndash862 2009

[56] G A Blanc A Schruba N J I Evans et al et al ldquoThe virus-Pexploration of nearby glaxies (venga) the X co gradient in NGC628rdquoThe Astrophysical Journal vol 764 article 117 2013

[57] S M Croom J S Lawrence J Bland-Hawthorn et al ldquoTheSydney-AAOMulti-object Integral field spectrographrdquoMonthlyNotices of the Royal Astronomical Society vol 421 no 1 pp 872ndash893 2012

[58] R Bacon S M Bauer R Bower et al et al ldquoThe second gen-eration VLT instrument MUSE science drivers and instrumentdesignrdquo in Groundbased Instrumentation for Astronomy A FM Moorwood and I Masanori Eds Proceedings of the SPIEpp 1145ndash1149 Observatoire de Lyon Lyon France 2004

[59] A M N Ferguson J S Gallagher and R F G Wyse ldquoTheExtreme Outer Regions of Disk Galaxies I Chemical Abun-dances of HII Regionsrdquo Astronomical Journal vol 116 article673 1998

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


FluidsJournal of

Atomic and Molecular Physics

Journal of



Advances in Condensed Matter Physics

OpticsInternational Journal of



AstronomyAdvances in

International Journal of


Superconductivity


Statistical MechanicsInternational Journal of


GravityJournal of


AstrophysicsJournal of


Physics Research International


Solid State PhysicsJournal of

Computational Methods in Physics

Journal of



Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014


PhotonicsJournal of


Journal of

Biophysics


ThermodynamicsJournal of


abundance and their relations with global galaxy parame-ters in high redshift galaxies (eg [5 6]) objects that aretypically solely identifiable by their emission line spectraNearby galaxies offer a unique opportunity to study theSFH-ISM coupling on a spatially resolved basis over largedynamic ranges in gas density and pressure metallicity dustcontent and other physically relevant parameters of gas anddust However most of the observations targeting nebularemission in nearby galaxies have beenmadewithmultibroad-band and narrow-band imaging in the optical and near-infrared or single-aperture or long-slit spectrographs result-ing in samples of typically a dozen or fewer HII regionsper galaxy These observations have been used to derivethe properties of their dominant stellar populations gascontent and kinematics (eg [7ndash9]) Nevertheless despitemany efforts it has been difficult to obtain a complete pictureof the main properties of these galaxies especially those onesthat can only be revealed by spectroscopic studies (like thenature of the ionization andor the metal content of the gas)This is because previous spectroscopic studies only sampleda very few discrete regions in these complex targets (eg[10 11]) or used narrow-band imaging of specific fields toobtain information of star-forming regions and the ionizedgas (eg [9]) and in many cases they were sampling veryparticular types of regions [12ndash15] Integrated spectra overlarge apertures were required to derive these properties ina more complete way (eg drift-scanning [16]) but even inthese cases only a single integrated spectrum is derived andthe spatial information is lost

On the other hand although large spectroscopic surveyslike the 2dFGRS or the SDSS do provide a large numberof objects sampled and vast statistical information they aregenerally limited to one spectrum per galaxy thus missingall the radial information and spatially resolved propertiesof the galaxy These surveys have been successful to describethe integrated properties and relations of a large number ofgalaxies along a wide redshift range But galaxies are complexsystems not fully represented by a single spectrum or justbroad band colours Disc and spheroidal components arestructurally and dynamically different entities with differentSFH and chemical evolution A main drawback of this tech-nique is that it leads to aperture bias that is difficult to controlas the area covered to integrate the spectra corresponds todifferent physical scales at different redshifts (eg SDSS)and also the physical mechanisms involved in ionizing thegas may be very different within the sampled area as thiswould include regions with emission due to diffuse ionizedgas (DIG) shocks or AGNLINER activity

The advent of Multi-Object Spectrometers (MOS) andIntegral Field Spectroscopy (IFS) instruments with largefields of view (FoV) now offers us the opportunity toundertake a new generation of surveys based on a full two-dimensional (2D) coverage of the optical extent of nearbygalaxies The first application of IFS to obtain spatiallyresolved continuously sampled spectroscopy of certain por-tions of nearby galaxies was due to the SAURON project[17 18] SAURON was specifically designed to study thekinematics and stellar populations of a sample of nearbyelliptical and lenticular galaxiesThe application of SAURON

to spiral galaxies was restricted to the study of spiral bulges[19] However IFS was rarely used in a ldquosurvey moderdquo toinvestigate sizeable samples There were several reasons forthe lack of a systematic study targeting galaxies in the localUniverse using IFS that could cover a substantial fraction oftheir optical sizes The reasons included small wavelengthcoverage fibre-optic calibration problems but mainly thelimited FoV of the instruments available worldwide MostIFUs have a FoV of the order of arcsec preventing a goodcoverage of the target galaxies on the sky in a reasonabletime even with a mosaicking technique Furthermore insome cases the emission lines used in chemical abundancestudies were not covered by the restrictedwavelenght range ofthe instruments Moreover the complex data reduction andvisualisation imposed a further obstacle

In order to fill this gap in the last few years we starteda major observational programme aimed at studying the2D properties of the ionized gas and HII regions in arepresentative sample of nearby face-on spiral galaxies usingIFS The spatially resolved information provided by theseobservations is allowing us to test and extend the previousbody of results from small-sample studies while at the sametime it opens up a new frontier of studying the 2D gasabundance on discs and the intrinsic dispersion inmetallicityprogressing from a one-dimensional study (radial abundancegradients) to a 2D understanding (distributions) allowing usat the same time to strengthen the diagnostic methods thatare used to measure HII region abundance in galaxies

Here we present the highlights of our current studiesemploying this large spectroscopic database (1) the case ofNGC628 the largest galaxy ever sampledwith IFS (2) an IFS-based statistical approach to the abundance gradients of spiralgalaxies and (3) the discovery of a new scaling relation of HIIregions in spiral galaxies and how we use it to to reproducemdashwith remarkable agreementmdashthe mass-metallicity relation ofstar-forming galaxies

2 A IFS Sample of Nearby Disc Galaxies

The studies here described were performed using IFS dataof a sample of nearby disc galaxies The observations weredesigned to obtain continuous coverage spectra of the wholesurface of the galaxies They include observations from thePPAK IFSNearby Galaxies Survey PINGS [20] and a sampleof face-on spiral galaxies fromMarmol-Queralto et al [21] aspart of the feasibility studies for the CALIFA survey [22 23]a legacy project which aims to observe a statistically completesample of sim600 galaxies in the local Universe all projects arecarried out at the Centro Astronomico Hispano-Aleman ofCalar Alto Spain

PINGS represented the first attempt to obtain continuouscoverage spectra of the whole surface of a representativesample of late-type galaxies in the nearby Universe Thisfirst sample includes normal lopsided interacting and barredspirals with a good range of galactic properties and star-forming environments with available multiwavelength publicdata (eg see Figure 1)The second sample consists of visuallyclassified face-on spirals from Marmol-Queralto et al [21]


NGC 1637

NGC 628

10998400

10998400

74998400998400

74998400998400

65998400998400

65998400998400

(a)

UGC 12250 UGC 233

UGC 5100CGCG 430-046

(b)










200

100

100

0

0

minus100

minus100

minus200

minus200

ΔD

ec (a

rcse

c)

ΔRA (arcsec)

NGC 628

E

N

(a)

200

100

0

minus100

100 0 minus100

Δ120572 (arcsec)Δ120575

(arc

sec)

12 + log(OH) [O3N2]90

88

86

84

82

(b)


















02 ≲ 120588120588








0 5 10 15 20 25

95

90

85

80

00 05 10 15



12+

log(

OH

) [O

3N2]

Radius 12058812058825

(a)

KK04

H13

12058825

200

100

100200

0

0

minus100

minus100

minus200

minus200

ΔD

ec (a

rcse

c)

ΔRA (arcsec)

E

N

+02dex+0100

minus01

minus02

(b)




120588=0412058825of the same




25






15

10

00

00

05

05

minus05

minus05

minus10


log(

[O II

I]1205825007

H120573

)

log([N II]1205826584H120572)

(a)

00 02 04 06 08 10

minus20

minus25

minus30

minus35

minus40

minus45


Radius 12058812058825lo

g u

(b)







1000

975

950

925

900

875

850

825


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)

Dec

(J20

00)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(a)

99

102

96

93

90

87

84

81

78


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)D

ec (J

2000

)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(b)










+lo

g(O

H)

9

88

86

84

0 05 1 15 2

minus084

minus021

040

103

log(

O3N





RRe


















90

85

12+

log(

OH

) [O

3N2]

1 10 100 1000ΣLum (M⊙ pcminus2)

(a)

90

85

12+

log(

OH

) [O

3N2]

1 10

NGC 1058UGC 9965UGC 3091

100 1000

log|

EW(H120572)|


(b)


12+

log(

OH

)

90

88

86

84

82

0000 0505

1010

15

15

20

20

25

25 30 35 log|EW

(120572)|

(A)


(a)

12+

log(

OH

)

9

85

8

75


107 108 109 1010 1011 1012

MLum (M⊙)

(b)







6 Conclusions





25) although with a







Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




NGC 1637

NGC 628

10998400

10998400

74998400998400

74998400998400

65998400998400

65998400998400

(a)

UGC 12250 UGC 233

UGC 5100CGCG 430-046

(b)










200

100

100

0

0

minus100

minus100

minus200

minus200

ΔD

ec (a

rcse

c)

ΔRA (arcsec)

NGC 628

E

N

(a)

200

100

0

minus100

100 0 minus100

Δ120572 (arcsec)Δ120575

(arc

sec)

12 + log(OH) [O3N2]90

88

86

84

82

(b)


















02 ≲ 120588120588








0 5 10 15 20 25

95

90

85

80

00 05 10 15



12+

log(

OH

) [O

3N2]

Radius 12058812058825

(a)

KK04

H13

12058825

200

100

100200

0

0

minus100

minus100

minus200

minus200

ΔD

ec (a

rcse

c)

ΔRA (arcsec)

E

N

+02dex+0100

minus01

minus02

(b)




120588=0412058825of the same




25






15

10

00

00

05

05

minus05

minus05

minus10


log(

[O II

I]1205825007

H120573

)

log([N II]1205826584H120572)

(a)

00 02 04 06 08 10

minus20

minus25

minus30

minus35

minus40

minus45


Radius 12058812058825lo

g u

(b)







1000

975

950

925

900

875

850

825


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)

Dec

(J20

00)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(a)

99

102

96

93

90

87

84

81

78


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)D

ec (J

2000

)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(b)










+lo

g(O

H)

9

88

86

84

0 05 1 15 2

minus084

minus021

040

103

log(

O3N





RRe


















90

85

12+

log(

OH

) [O

3N2]

1 10 100 1000ΣLum (M⊙ pcminus2)

(a)

90

85

12+

log(

OH

) [O

3N2]

1 10

NGC 1058UGC 9965UGC 3091

100 1000

log|

EW(H120572)|


(b)


12+

log(

OH

)

90

88

86

84

82

0000 0505

1010

15

15

20

20

25

25 30 35 log|EW

(120572)|

(A)


(a)

12+

log(

OH

)

9

85

8

75


107 108 109 1010 1011 1012

MLum (M⊙)

(b)







6 Conclusions





25) although with a







Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




200

100

100

0

0

minus100

minus100

minus200

minus200

ΔD

ec (a

rcse

c)

ΔRA (arcsec)

NGC 628

E

N

(a)

200

100

0

minus100

100 0 minus100

Δ120572 (arcsec)Δ120575

(arc

sec)

12 + log(OH) [O3N2]90

88

86

84

82

(b)


















02 ≲ 120588120588








0 5 10 15 20 25

95

90

85

80

00 05 10 15



12+

log(

OH

) [O

3N2]

Radius 12058812058825

(a)

KK04

H13

12058825

200

100

100200

0

0

minus100

minus100

minus200

minus200

ΔD

ec (a

rcse

c)

ΔRA (arcsec)

E

N

+02dex+0100

minus01

minus02

(b)




120588=0412058825of the same




25






15

10

00

00

05

05

minus05

minus05

minus10


log(

[O II

I]1205825007

H120573

)

log([N II]1205826584H120572)

(a)

00 02 04 06 08 10

minus20

minus25

minus30

minus35

minus40

minus45


Radius 12058812058825lo

g u

(b)







1000

975

950

925

900

875

850

825


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)

Dec

(J20

00)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(a)

99

102

96

93

90

87

84

81

78


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)D

ec (J

2000

)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(b)










+lo

g(O

H)

9

88

86

84

0 05 1 15 2

minus084

minus021

040

103

log(

O3N





RRe


















90

85

12+

log(

OH

) [O

3N2]

1 10 100 1000ΣLum (M⊙ pcminus2)

(a)

90

85

12+

log(

OH

) [O

3N2]

1 10

NGC 1058UGC 9965UGC 3091

100 1000

log|

EW(H120572)|


(b)


12+

log(

OH

)

90

88

86

84

82

0000 0505

1010

15

15

20

20

25

25 30 35 log|EW

(120572)|

(A)


(a)

12+

log(

OH

)

9

85

8

75


107 108 109 1010 1011 1012

MLum (M⊙)

(b)







6 Conclusions





25) although with a







Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics













02 ≲ 120588120588








0 5 10 15 20 25

95

90

85

80

00 05 10 15



12+

log(

OH

) [O

3N2]

Radius 12058812058825

(a)

KK04

H13

12058825

200

100

100200

0

0

minus100

minus100

minus200

minus200

ΔD

ec (a

rcse

c)

ΔRA (arcsec)

E

N

+02dex+0100

minus01

minus02

(b)




120588=0412058825of the same




25






15

10

00

00

05

05

minus05

minus05

minus10


log(

[O II

I]1205825007

H120573

)

log([N II]1205826584H120572)

(a)

00 02 04 06 08 10

minus20

minus25

minus30

minus35

minus40

minus45


Radius 12058812058825lo

g u

(b)







1000

975

950

925

900

875

850

825


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)

Dec

(J20

00)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(a)

99

102

96

93

90

87

84

81

78


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)D

ec (J

2000

)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(b)










+lo

g(O

H)

9

88

86

84

0 05 1 15 2

minus084

minus021

040

103

log(

O3N





RRe


















90

85

12+

log(

OH

) [O

3N2]

1 10 100 1000ΣLum (M⊙ pcminus2)

(a)

90

85

12+

log(

OH

) [O

3N2]

1 10

NGC 1058UGC 9965UGC 3091

100 1000

log|

EW(H120572)|


(b)


12+

log(

OH

)

90

88

86

84

82

0000 0505

1010

15

15

20

20

25

25 30 35 log|EW

(120572)|

(A)


(a)

12+

log(

OH

)

9

85

8

75


107 108 109 1010 1011 1012

MLum (M⊙)

(b)







6 Conclusions





25) although with a







Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




0 5 10 15 20 25

95

90

85

80

00 05 10 15



12+

log(

OH

) [O

3N2]

Radius 12058812058825

(a)

KK04

H13

12058825

200

100

100200

0

0

minus100

minus100

minus200

minus200

ΔD

ec (a

rcse

c)

ΔRA (arcsec)

E

N

+02dex+0100

minus01

minus02

(b)




120588=0412058825of the same




25






15

10

00

00

05

05

minus05

minus05

minus10


log(

[O II

I]1205825007

H120573

)

log([N II]1205826584H120572)

(a)

00 02 04 06 08 10

minus20

minus25

minus30

minus35

minus40

minus45


Radius 12058812058825lo

g u

(b)







1000

975

950

925

900

875

850

825


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)

Dec

(J20

00)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(a)

99

102

96

93

90

87

84

81

78


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)D

ec (J

2000

)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(b)










+lo

g(O

H)

9

88

86

84

0 05 1 15 2

minus084

minus021

040

103

log(

O3N





RRe


















90

85

12+

log(

OH

) [O

3N2]

1 10 100 1000ΣLum (M⊙ pcminus2)

(a)

90

85

12+

log(

OH

) [O

3N2]

1 10

NGC 1058UGC 9965UGC 3091

100 1000

log|

EW(H120572)|


(b)


12+

log(

OH

)

90

88

86

84

82

0000 0505

1010

15

15

20

20

25

25 30 35 log|EW

(120572)|

(A)


(a)

12+

log(

OH

)

9

85

8

75


107 108 109 1010 1011 1012

MLum (M⊙)

(b)







6 Conclusions





25) although with a







Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




15

10

00

00

05

05

minus05

minus05

minus10


log(

[O II

I]1205825007

H120573

)

log([N II]1205826584H120572)

(a)

00 02 04 06 08 10

minus20

minus25

minus30

minus35

minus40

minus45


Radius 12058812058825lo

g u

(b)







1000

975

950

925

900

875

850

825


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)

Dec

(J20

00)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(a)

99

102

96

93

90

87

84

81

78


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)D

ec (J

2000

)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(b)










+lo

g(O

H)

9

88

86

84

0 05 1 15 2

minus084

minus021

040

103

log(

O3N





RRe


















90

85

12+

log(

OH

) [O

3N2]

1 10 100 1000ΣLum (M⊙ pcminus2)

(a)

90

85

12+

log(

OH

) [O

3N2]

1 10

NGC 1058UGC 9965UGC 3091

100 1000

log|

EW(H120572)|


(b)


12+

log(

OH

)

90

88

86

84

82

0000 0505

1010

15

15

20

20

25

25 30 35 log|EW

(120572)|

(A)


(a)

12+

log(

OH

)

9

85

8

75


107 108 109 1010 1011 1012

MLum (M⊙)

(b)







6 Conclusions





25) although with a







Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




1000

975

950

925

900

875

850

825


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)

Dec

(J20

00)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(a)

99

102

96

93

90

87

84

81

78


50998400000998400998400

49998400000998400998400

48998400000998400998400

47998400000998400998400

46998400000998400998400

45998400000998400998400

+15∘44998400000998400998400

RA (J2000)D

ec (J

2000

)

5500

s

5000

s

4500

s

4000

s

3500

s

1h3

6m3000

s

(b)










+lo

g(O

H)

9

88

86

84

0 05 1 15 2

minus084

minus021

040

103

log(

O3N





RRe


















90

85

12+

log(

OH

) [O

3N2]

1 10 100 1000ΣLum (M⊙ pcminus2)

(a)

90

85

12+

log(

OH

) [O

3N2]

1 10

NGC 1058UGC 9965UGC 3091

100 1000

log|

EW(H120572)|


(b)


12+

log(

OH

)

90

88

86

84

82

0000 0505

1010

15

15

20

20

25

25 30 35 log|EW

(120572)|

(A)


(a)

12+

log(

OH

)

9

85

8

75


107 108 109 1010 1011 1012

MLum (M⊙)

(b)







6 Conclusions





25) although with a







Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




+lo

g(O

H)

9

88

86

84

0 05 1 15 2

minus084

minus021

040

103

log(

O3N





RRe


















90

85

12+

log(

OH

) [O

3N2]

1 10 100 1000ΣLum (M⊙ pcminus2)

(a)

90

85

12+

log(

OH

) [O

3N2]

1 10

NGC 1058UGC 9965UGC 3091

100 1000

log|

EW(H120572)|


(b)


12+

log(

OH

)

90

88

86

84

82

0000 0505

1010

15

15

20

20

25

25 30 35 log|EW

(120572)|

(A)


(a)

12+

log(

OH

)

9

85

8

75


107 108 109 1010 1011 1012

MLum (M⊙)

(b)







6 Conclusions





25) although with a







Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




90

85

12+

log(

OH

) [O

3N2]

1 10 100 1000ΣLum (M⊙ pcminus2)

(a)

90

85

12+

log(

OH

) [O

3N2]

1 10

NGC 1058UGC 9965UGC 3091

100 1000

log|

EW(H120572)|


(b)


12+

log(

OH

)

90

88

86

84

82

0000 0505

1010

15

15

20

20

25

25 30 35 log|EW

(120572)|

(A)


(a)

12+

log(

OH

)

9

85

8

75


107 108 109 1010 1011 1012

MLum (M⊙)

(b)







6 Conclusions





25) although with a







Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics






6 Conclusions





25) although with a







Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics








Acknowledgments



References




































































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics























































FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics



















FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics








FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics



Documents

The Study of Nebular Emission on Nearby Spiral Galaxies in the IFU