The Dusty and Molecular Universe ----- October 2004 Chemical
evolution of the envelopes of intermediate-mass young stellar
objects (YSOs): NGC 7129-FIRS 2 and LkH 234 Asuncin Fuente, Ricardo
Rizzo, Roberto Neri, Paola Caselli, Rafael Bachiller Slide 2 The
Dusty and Molecular Universe ---- October 2004 Standard model of
star formation 1. Formation of pre-stellar clumps in molecular
clouds. 2. The pre-stellar clump collapses 3. Protostar (infall and
outflow coexists) 4. Formation of a planetary system Fig. from
McCaughrean Slide 3 The Dusty and Molecular Universe ---- October
2004 Standard model of star formation We need to find objects at
different evolutionary stage to be able to study the star formation
process. Some Problems: Different star formation processes for
stars with different masses. We need a clock for young stellar
objects (YSOs). The star formation process could depend on the
molecular cloud initial conditions. YSOs at different distances are
sampled at different spatial scale. Slide 4 The Dusty and Molecular
Universe ---- October 2004 Chemistry as a clock for YSOs 13 CO C 18
O C 17 O H 13 CO + N2H+N2H+ NH 3 CH 3 OH H 2 CO HCOOH CH 3 CN SiO
SO CH 3 OH CNHCN C 2 H 3 CN C 2 H 5 CN Slide 5 The Dusty and
Molecular Universe ---- October 2004 Some problems In addition to
the evolutionary stage of the protostar, chemical changes also
depend on the final stellar mass. Thus, the chemical composition of
the hot core is dependent on the kinetic temperature of the gas
(see e.g. Rodgers & Charnley 2003). High mass star creates a
PDR or HII region around them. Chemical changes also depend on the
initial chemical conditions of the molecular cloud, i.e., the
chemical composition of the gas and icy mantles(see e.g. Maret et
al. 2004, Wakelam et al. 2004) Robust chemical diagnostics are
required. Slide 6 The Dusty and Molecular Universe ---- October
2004 Sample Selection Why NGC 7129 - FIRS 2 and LkH 234? They are
located in the same molecular cloud, minimizing the chemical
differences because of different initial chemical conditions. They
are located at a distance of 1250 pc. Both have similar
luminosities (~ 500 L sun ). LkH 234 is one of the youngest HBe
star (Sp. type = B3). NGC 7129 - FIRS 2 is a Class 0 object. Slide
7 The Dusty and Molecular Universe ---- October 2004 NGC 7129-FIRS
2 and LkH 234 Sp. typeB5-7 Age0.1 Myr OutflowNo LkH 234
NGC7129-FIRS 2 Lum500 L o Age>3000 yr OutflowYes Continuum 1.3mm
Slide 8 The Dusty and Molecular Universe ---- October 2004
Observational Strategy Slide 9 The Dusty and Molecular Universe
---- October 2004 Physical conditions Two gas components in NGC
7129-FIRS 2 and LkH 234: -Cold component: v~1 kms -1, Tk3 kms -1,
Tk>50 K. The column density of the cold component decreases by
an order of magnitude between NGC 7129-FIRS 2 and LkH 234, while
the mean kinetic temperature increases from 13 K to 28 K. Slide 10
The Dusty and Molecular Universe ---- October 2004 Single-dish maps
NGC 7129-FIRS 2 LkH 234 Slide 11 The Dusty and Molecular Universe
---- October 2004 Chemical evolution Cold envelope: Warm envelope:
Outflow: PDR: Slide 12 The Dusty and Molecular Universe ----
October 2004 Chemical clocks These abundance ratios are averaged
values in the protostellar envelopes. Thus, they do not correspond
to values of the molecular abundances any part of the envelope. In
general, they reveal the relative importance of the different
envelope components. Complex behavior Slide 13 The Dusty and
Molecular Universe ---- October 2004 SiO NGC 7129-FIRS 2 LkH 234
NGC 7129-FIRS 2 out 1 out 2 In NGC 7129-FIRS 2, the SiO emission is
detected along the outlows axis. The peak emission is found towards
the bullet R1 at a velocity of 7 km s -1. In LkHa234, SiO is only
detected towards the star position. Slide 14 The Dusty and
Molecular Universe ---- October 2004 SiO There is a correlation
between the outflow ages and the SiO abundance, being the SiO
abundance largest in the youngest outflow FIRS 2-out 1. The SiO
abundance in LkHa 234 is similar to that found in photodissociation
regions (PDRS). Slide 15 The Dusty and Molecular Universe ----
October 2004 H 2 CO In NGC 7129-FIRS 2, the H 2 CO emission arises
in the jet (wide component) and the shocked gas of the molecular
cloud. Slide 16 The Dusty and Molecular Universe ---- October 2004
CH 3 OH The CH 3 OH column density is similar in both YSOs. In NGC
7129-FIRS 2 the emission arises in the outflow.Is there a hot core
component? Hot core? NGC 7129 - FIRS 2 Slide 17 The Dusty and
Molecular Universe ---- October 2004 CH 3 CN A hot component in the
CH 3 CN emission suggests the existence of a hot core in NGC 7129 -
FIRS 2. Slide 18 The Dusty and Molecular Universe ---- October 2004
Interferometric observations (PdBI) in NGC 7129-FIRS 2 Single-dish
observations provide information on the physical and chemical of
the cold protostellar envelope. Interferometric observations are
required to study the physical and chemical structure of the warm
inner protostellar envelope. Continuum 3mmA1.56x1.2 arcsec
Continuum 1mmA0.63x0.46 arcsec CH 3 CN 5-4A1.56x1.2 arcsec N 2 D +
3-2A0.63x0.46 arcsec D 2 CO 4 04 -3 03 A0.63x0.46 arcsec CH 3 OH
5-4CD1.51x1.42 arcsec Slide 19 The Dusty and Molecular Universe
---- October 2004 Continuum observations (PdBI) Intense and compact
continuum source RA(2000)=21:43:01.68 Dec(2000)=66:03:23.62 The
same spatial distribution at 3mm and 1mm, with a spectral index
=2.56 consistent with thermal dust emission. Slide 20 The Dusty and
Molecular Universe ---- October 2004 Continuum observations (PdBI)
Elliptical Gaussian RA=21:43:01.7 Dec=66:03:23.7 Major=0.72(0.01)
arcseconds Minor=0.52(0.01) arcseconds Flux= 0.43 Jy Point source
RA=21:43:01.7 Dec=66:03:23.7 Flux=0.13 Jy Slide 21 The Dusty and
Molecular Universe ---- October 2004 Molecular line observations
(PdBI) Undetected Hot core Slide 22 The Dusty and Molecular
Universe ---- October 2004 A chemistry rich in complex molecules(I)
Slide 23 The Dusty and Molecular Universe ---- October 2004 A
chemistry rich in complex molecules(II) Slide 24 The Dusty and
Molecular Universe ---- October 2004 CH 3 CN observations (PdBI)
Hot core component Size = 800 AU x 600 AU Mass= 2 M o X(CH 3 CN) =
2.3 10 -8 Cold envelope component Size ~ 0.2 pc Mass~ 16 M o X(CH 3
CN) = 1.4 10 -11 Our interferometric observartions unambiguously
show the existence of a hot core in the IM protostar NGC 7129-FIRS
2. The chemistry of the hot core is enriched in complex oxygenated
compounds (CH 3 OH, HCOOH, CH 3 OCHO-A and CH 3 OCHO-E),
nitrogen-bearing molecules (CH 3 CN,C 2 H 5 CN,HOONO 2 ?), sulphur-
bearing species (S 18 O,OCS, 13 CS,H 2 13 CS?), and deuterated
molecules (D 2 CO,c-C 3 D,c-C 3 HD). Slide 25 The Dusty and
Molecular Universe ---- October 2004 Conclusions NGC 7129-FIRS 2 is
the first hot core detected in an intermediate mass YSOs with a
size ~600 AU. So far, two hot cores have been detected in low mass
stars (IRAS 16293-2422: Cazaux et al. 2003; NGC 1333-FIRS 4A.
Bottinelli et al. 2004) with sizes ~150 AU. The size and chemical
complexity detected in NGC 7129-FIRS 2 suggest that this is an
intermediate object between the low-mass stars and high-mass hot
cores. There are morphological and kinematic evidences of an
internal structure of the hot core. But the high angular resoludion
provided by ALMA is required to study it. Slide 26 The Dusty and
Molecular Universe ---- October 2004 The HIFI intermediate-mass
team Asuncin FUENTE, Observatorio Astronmico Nacional (Spain)
Cecilia CECCARELLI, Observatoire de Grenoble (France) Paola
CASELLI, Osservatorio Astrofisico di Arcetri (Italy) Doug
JOHNSTONE, NRC (Canada) Ewine VAN DISHOECK, Leiden Observatory
(Netherlands) Ren PLUME, University of Calgary (Canada) Bertrand
LEFLOCH, Observatoire de Grenoble (France) Friedrich WYROWSKI,
MPIfR (Germany) Mario TAFALLA, Observatorio Astronmico Nacional
(Spain) Brunela NISINI, Italy Main goals: Preparatory observations
for the HIFI core programme (SCUBA, JCMT, IRAM, Effelsberg)
Preparatory observations for ALMA (PdBI)
