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)
de Gregorio-Monsalvo, SOCHIAS 2009 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: - Linewidthsand 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.
L1521E B68 (Lai et al. 2003) (Hirota et al. 2002) de Gregorio-Monsalvo, SOCHIAS 2009 Why CCS is interesting? • Evolutionary effect: Star formation phenomena destroy CCS BUT favor ammonia production. Previous works:Starless cores, single-dish observations. What about (more evolved) star-forming regions at higher resolution?
RESULT: 6 detections in CCS and NH3 (de Gregorio-Monsalvo et al. 2006) 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)
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
CO(1-0) 2MASS + H2O masers (Hirano et al. 1997) (de Gregorio-Monsalvo et al. 2005) 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). • 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 ).
CCS Vlsr 10000 AU at 350 pc (de Gregorio-Monsalvo et al. 2005) de Gregorio-Monsalvo, SOCHIAS 2009 B1-IRS: CCS emission • CCS emission is clumpy. • Redshifted clumps. • Velocity gradient blue- • shifted towards the • central source
CCS Vlsr 10000 AU at 350 pc (de Gregorio-Monsalvo et al. 2005) (de Gregorio-Monsalvo et al. 2005) de Gregorio-Monsalvo, SOCHIAS 2009 B1-IRS: CCS emission - Strong interaction with the molecular outflow - CCS enhanced via shocked induced chemistry?
(de Gregorio-Monsalvo et al. 2005) NH3 CCS de Gregorio-Monsalvo, SOCHIAS 2009 B1-IRS: Ammonia vs CCS • Spatial anticorrelation at scales of ~5’’ • Useful for testing future theoretical chemical models
L1448-IRS3 Blue L1448-IRS2 L1448C Red de Gregorio-Monsalvo, SOCHIAS 2009 L1448 • 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 Vlsr L1448C H2O CCS (contours) + IR outflow (gray) H2O masers
L1448-IRS3 L1448C de Gregorio-Monsalvo, SOCHIAS 2009 L1448: CCS emission • CCS emission is clumpy. • Strong interaction between CCS clumps and the outflows. 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)
Vlsr Vlsr de Gregorio-Monsalvo, SOCHIAS 2009 L1448: Kinematics CCS (contours + color) 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!
Before Before VLA-D VLA-B Continuum at 1.3 cm Continuum at 1.3 cm + + After After 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). 3-5 3-7 (de Gregorio-Monsalvo et al. in prep.) Improvement of ~30% in the SNR ...cross-calibration on spectral lines is feasible!!!!