Chris Salter (NAIC – Arecibo)

NAIC-AUSAC Meeting April 19 & 20, 2010

Chris Salter (NAIC – Arecibo)

GALFA & GALFACTS

GALFA-HI and GALFACTS (Courtesy: Steven Gibson)


GALFA Sub-Consortia

• H I Line (GALFA-H I)

• Continuum (GALFA-CON = GALFACTS)

• Radio Recombination Lines (GALFA-RRL)

• Each GALFA sub-consortium has its own membership and internal organization.

• All GALFA data will be made public through the National Virtual Observatory.


RRL Galactic-Plane Survey

• Galactic Structure

• Chemical Abundances

• Warm Diffuse ISM

• HII Regions

• Survey for |b| < 5o

• Integration time of 300s

• Commensal with PALFA & ZoA projects

• Share a “Mock spectrometer” database with ZoA (Δv≈4 kms-1)

• Record H163α−H174α, plus He & C α-lines and H β-lines

• Co-add transitions to increase signal-to-noise

• “Leap-Frog” Pointing to provide ON/OFFs

(PI: Yervant Terzian)

(Terzian & Lewis)


GALFACTS (GALFA Continuum Transit Survey) • Full-Stokes, all-Arecibo-sky, continuum

survey.

• Employs meridian NODding scans with subsequent “multi-beam” basket-weaving to optimize zero-levels.

• Bandwidth = 300 MHz → Faraday tomography, Ip(x, y, RM).

• Use “winking cal” for best possible calibration.

• Use of an original multi-beam CLEAN.

• Calibration run in Oct 2008 was first scheduled observations with Mock spectrometers.

• First GALFACTS region (1h<RA<7h; 20°<δ<38°) observed Nov-Dec 2008.

(GALFACTS Pilot Survey)

Now also observed at 327 MHz (Raja et al.) to provide finer resolution in RM for Faraday Tomography)


Mapping Technique: ZA Nodding + AZ Wagging

ALFA beams

Tracks after several passes

These are “woven” together to optimize zerolevels.

• P.I.: Russ Taylor

• Web Page: www.ucalgary.ca/ras/GALFACTS

• 14400 channels over 300-MHz bandwidth with “Mock spectrometer”

• Brightness sensitivity: rms~100 μJy/bm

• Meridian scanning speed ~1.5° per sec

• CIMA “Smart Basket-weaving” used


GALFACTS (continued)• Catalog of Poln. Percentage, Position

Angle & RM for 50,000 sources → Galactic Magnetic Field Studies.

• Thermal-nonthermal separation of low-b Galactic continuum emission.

• Provide thermal brightnesses for use by GALFA-RRL.

• Studies of discrete Galactic radio sources (e.g. SNRs & HII regions).

• Studies of high-b Galactic Loops.

• Foreground removal for EoR and Planck full-Stokes CMB studies.

• GALFA-HI TOG2 commensal project.

• First GALFACTS look at the Galactic Center quadrant via commensal observations with I-GALFA. (GALFACTS precursor imaging of the

Perseus Molecular Cloud region)


GALFA-HI Pointing Record as of 2008 March 14

GALSPECT has 8192 channels over 7.14 MHz → 0.18 km/s/channel, and ± 750 km/s total coverage

GALFA-H I ObservationsGALFA-HI Pointing Record as of 2009 February 26


GALFA H I Projects

a2186/2144/2390

a2048/2059a2010/2059a2130/2124

a2056/2051a2060

a2055

a2034

a1943

a2004

a2174/2294

a2221

ALFALFA/TOGS1 AGES/TOGS1 GALFACTS/TOGS2

I-GALFA/ZOA/ GALFACTS2 DISK-

HALOMBW/ZOA

PERSEUS

TAURUS

HALOCLOUDS

WINGS

a2220

a2222a2187

a2050

a2011 a2011a2172

a2172

a2147a2032

TIP MAGSTREAM GEM

OB1

TRUE FIL

SHELL

HIGH-LAT CLOUDS

HIGH-LATTURBULENCE

WATER FALL

OUTER HALO

PRECURSOR

COLDCLOUD

(Trms ~ 0.25 K)

(Trms ~ 0.15 K) (Trms ~ 0.04 K) (Trms ~ 0.35 K)


CGPSVGPS

SGPS

I-GALFA Plane H I Survey

10 x IGPS sensitivity, 4 x velocity resolution

I-GALFA Survey: 2008-9


I-GALFA (low-b Galactic Center Quadrant)

(PI’s: Steven Gibson & Bon Chul Koo)

• Over 50% completed in 2008

• Full completion expected during 2009

• Commensal with GALFACTS2

Cold HI Absorption in Molecular Clouds

Cold HI Emission at Higher Latitudes

Disc-Halo Interface


HI near Globular Cluster, Pal 4(PI: Jacco van Loon)

•Earlier LBW study detected HI in metal-poor cluster, M15 (van Loon et al, 2006).

• New stringent HI upper limits placed on clusters M3, NGC 5466 & Pal 13.

• Pal 4 is the 2nd most distant known globular cluster (D = 109 kpc).

• Large HI HVC discovered near Pal 4. Is it coincidence, gas stripped from the cluster by interaction with halo gas, or could both be situated in a 108 Mo dark halo?


An IVC Towards Abell 1367(PI: Kevin Douglas)

• Commensal GALFA-HI observations with EALFA-AGES of 10 fields.

• The Abell 1367 field is at b ≈ 70°−75°, and reveals possibly cometary IVCs.

• Brightness temperatures of the features are only 1K or less!


The Three Little Pigs (and a Friend)(PI: Josh Goldston Peek)

• Tiny clouds found at b ≈ 85°; Δθ ≈ 1'.

• VLA follow-up shows condensed cores , optically-thick, with TB ≈ 10K.

• Upper limits on OH emission from Arecibo.


GALFA Summary• Small GALFA-H I projects completed

• 3 Sub-Consortia (GALFA-H I, -CON, -RRL)

• TOGS1&2 in progress; data analysis on-going

• I-GALFA and GALFACTS in progress

• GALFA-RRL/ZOA/PALFA starting soon

• All final GALFA datasets will be on NVO

• GALFA website: www.naic.edu/alfa/galfa


End


GALFA - H I Projects

56% Mar 1716% Mar 1778% Mar 17

start ASAP

start May 3


Full-Stokes Multibeam CLEAN

(S. Guram,MSc Thesis,U. Calgary)

Stokes IDirty Image

MultibeamClean Image(HPBW=3.5°)

NVSSComparison(HPBW=0.7°)

Documents

Chris Salter (NAIC – Arecibo)