Transcript de Gregorio-Monsalvo et al. 2005

Ammonia and CCS as diagnostic tools of
low-mass protostars
Itziar de Gregorio-Monsalvo
(ESO /ALMA fellow in Chile)
Collaborators: J.F. Gómez (IAA, Spain)
C.J. Chandler (NRAO, USA)
T.B.H. Kuiper (JPL-Caltech, USA)
J.M. Torrelles (IEEC, Spain)
G. Anglada (IAA, Spain)
Molecular lines as diagnosis tools of the
interestellar medium
Physical conditions:
- The excitation conditions depend on TK, n H2 and the radiation field.
- Molecular clouds:
TK ~ 10 K → excites lowest rotational transitions
- From line intensities: Tex, τ, N
Kinematics:
- Linewidths and shapes→ turbulent and systemic motions of the gas
Stage of evolution:
- Time-dependent chemistry and the spatial distribution of some species
(e.g. NH3 (late-type molecule) and CCS (early-type molecule)).
de Gregorio-Monsalvo, SOCHIAS 2009
Why CCS is interesting?
“CCS spectral lines are a powerful tool to study YSOs”
1. High density gas tracer:
• Structure and physical conditions of the cloud.
• Intense in cold quiescent cores.
2. Kinematics:
• No splitting in hyperfine structure
3. Evolutionary stage of molecular clouds.
• Spatial anticorrelation between CCS and ammonia.
• [CCS] / [NH3] indicator of cloud evolution.
de Gregorio-Monsalvo, SOCHIAS 2009
Why CCS is interesting?
• Evolutionary effect: Star formation phenomena destroy CCS
BUT favor ammonia production.
L1521E
(Hirota et al. 2002)
B68
(Lai et al. 2003)
Previous works: Starless cores, single-dish observations.
What about (more evolved) star-forming regions at higher resolution?
de Gregorio-Monsalvo, SOCHIAS 2009
CCS and NH3 survey in low-mass star forming
regions (SFRs)
GOALS:
1- Find good candidates for interferometric observations.
2- Relation between CCS and physical characteristics and age of
star forming regions.
SURVEY: 40 young low-mass star forming
regions using the Robledo-70m (NASA
DSS-63) antenna at 22 GHz (1cm).
SELECTION CRITERIA: Low-mass regions with presence of H2O maser
emission at 22 GHz (traces star formation activity and youth; Furuya 2001)
RESULT: 6 detections in CCS and NH3 (de Gregorio-Monsalvo et al. 2006)
de Gregorio-Monsalvo, SOCHIAS 2009
Survey conclusions
• Dependencies of CCS emission on source and cloud parameters (stadistical study):
- No relation with source luminosity, radio continuum and water maser
flux densities, nor with molecular outflows parameters (RC, M, , LCO,
P, F, Ekin).
- CCS emitting regions show NH3 spectrum with narrow v
→ less turbulence, younger regions
• Ammonia linewidths broader than CCS ones:
- CCS and ammonia trace different regions
de Gregorio-Monsalvo, SOCHIAS 2009
VLA interferometric observations
Observations at ~1.3cm (22 GHz)
in CCS, H2O, and NH3
Very Large Array, New Mexico (USA).
GOALS : 1- Study physical conditions, kinematics, and interaction with the
medium at high-angular resolution.
2- Test the distribution of CCS vs. NH3 in SFRs at small scales
SOURCES : B1-IRS, L1448C and L1448-IRS3
de Gregorio-Monsalvo, SOCHIAS 2009
B1-IRS
• Class 0 source in Perseus (350 pc; Bachiller et al. 1990).
• CO (1-0) outflow (Hirano et al. 1997).
CO(1-0)
2MASS + H2O masers
(Hirano et al. 1997)
(de Gregorio-Monsalvo et al. 2005)
• 2MASS source at the tip of the CO outflow (reflection nebula in K-band).
• H2O masers in an elongated structure. Unbound motions, probably tracing a jet .
• Lack of velocity gradient ( Outflow lies near the plane of the sky ).
de Gregorio-Monsalvo, SOCHIAS 2009
B1-IRS: CCS emission
CCS
• CCS emission is clumpy.
• Redshifted clumps.
Vlsr
10000 AU at 350 pc
• Velocity gradient blueshifted towards the
central source
(de Gregorio-Monsalvo et al. 2005)
de Gregorio-Monsalvo, SOCHIAS 2009
B1-IRS: CCS emission
CCS
Vlsr
10000 AU at 350 pc
(de Gregorio-Monsalvo et al. 2005)
- Strong interaction with the molecular outflow
- CCS enhanced via shocked induced chemistry?
de Gregorio-Monsalvo, SOCHIAS 2009
B1-IRS: Ammonia vs CCS
(de Gregorio-Monsalvo et al. 2005)
NH3
CCS
- Spatial anticorrelation at scales of ~5’’
- Useful for testing future theoretical chemical models
de Gregorio-Monsalvo, SOCHIAS 2009
L1448
L1448-IRS3
Blue
L1448-IRS2
L1448C
Red
• Located in Perseus molecular cloud (250 pc; Enoch et al. 2006).
• L1448-C (Class 0 source) and L1448-IRS3 (Class0/I source).
• Spectacular molecular outflow (Bachiller et al. 1990)
de Gregorio-Monsalvo, SOCHIAS 2009
L1448: CCS emission
Vlsr
H2O
L1448-IRS3
L1448C


CCS (contours) + IR outflow (gray)
Vlsr
H2 O
H2O masers
de Gregorio-Monsalvo, SOCHIAS 2009
L1448: CCS emission
L1448-IRS3
• CCS emission is clumpy.
• Strong interaction between CCS
clumps and the outflows.
L1448C


Again, the CCS seems to be enhanced
in shocked regions
CCS (contours) + IR outflow (gray)
(de Gregorio-Monsalvo et al. in prep.)
de Gregorio-Monsalvo, SOCHIAS 2009
L1448: CCS vs. NH3
Again: Spatial
anticorrelation
at scales of ~5’’
CCS (contours) and NH3(gray; Curiel et al. 1999)
de Gregorio-Monsalvo, SOCHIAS 2009
L1448: Kinematics
Vlsr
CCS (contours + color)
Vlsr
CCS (contours) + NH3 (color)
Again: CCS and NH3 show a kinematics associated with a strong
interaction with the molecular outflows of the region.
de Gregorio-Monsalvo, SOCHIAS 2009
General Conclusions
1. CCS and NH3 survey in low-mass SFRs → six sources show CCS and NH3
2. Statistical study:
- No relation between the characteristic of the central sources or the molecular
outflows and the presence of CCS.
- Relation with ammonia linewidth supports that the CCS-emiting regions might be
younger.
3. We observed a spatial anticorrelation between NH3 and CCS at scales of 5’’ → a
combination of both is needed to trace the full column density of dense material and to
understand the kinematics of the young SFRs.
4. CCS kinematical patterns suggests a strong interaction between the gas traced by CCS
and the molecular outflow of the region → a shocked induced chemistry could be
responsible for a local CCS abundance enhancement.
de Gregorio-Monsalvo, SOCHIAS 2009
Thank you!
de Gregorio-Monsalvo, SOCHIAS 2009
IRAS 16293-2422
Testing a new observation technique: cross-calibration in spectral line.
- Simultaneous observations of CCS (22.35 GHz) and H2O (22.24 GHz).
- Self-calibration of H2O masers to correct for atmospheric variations.
• No CCS emission, but averaging the central 93 channels, allowed to detect
radio continuum emission at ~1.3 cm (left panel).
Before
3-5 
After
VLA-D
Before
VLA-B
Continuum
at 1.3 cm
Continuum
at 1.3 cm
+
+
After
3-7 
(de Gregorio-Monsalvo et al. in prep.)
Improvement of ~30% in the SNR ...cross-calibration on spectral lines is feasible!!!!
de Gregorio-Monsalvo, SOCHIAS 2009