Interferometer Observations of Dense Gas in Protostellar Clusters

Identification of Super-Jeans CoresJames Di Francesco(thanks to S. Sadavoy, S. Chitsazzadeh, S. Mairs, S. Schnee, M. Chen, R. Friesen, H. Kirk, and the Herschel & JCMT GBS Teams)The Jeans Mass maximum mass MJ in radius RJ that is stable

spherical, non-rotating, non-magnetic, etc.

serves as a benchmark(MJ / M) = 2.9 (T / 10 K)1.5 (n / 104 cm-3)-0.5 = 1.9 (T / 10 K) (RJ / 0.07 pc)

RJMJCOLDCOMPACT&2Perturbations in masses above Mj will grow exponentially, leading to fragmentation or collapse.Nutter, Ward-Thompson & Andr (2006); Di Francesco et al. (2008)Detecting Super-Jeans Cores Starless super-Jeans cores are very promising sites to study the onset of collapse

Wide-field continuum surveys still the best way to locate such cores

SCUBA Legacy Catalogues at 850 m, Herschel, etc.

Ophiuchus (L1689-S)~0.1 pcSCUBA 850 m3Sadavoy, Di Francesco, & Johnstone (2010)Observed Super-Jeans Cores

Sadavoy et al. (2010) examined 729 SCUBA cores found in Ophiuchus, Perseus, Taurus, & OrionContours: 850 m (SCUBA)Greyscale: 8 m (IRAC)starlessstarlessundetermined4To determine starlessness need sensitive mid-IR to far-IR observations, e.g., 8 micron with IRAC, 70 micron with MIPS or Herschel.

Sadavoy, Di Francesco, & Johnstone (2010)Starless Super-Jeans Cores only 3 starless and 11 undetermined24.55Only about 2% of the SCUBA sample was found to be starless and super-Jeans.Sadavoy, Di Francesco, & Johnstone (2010)Starless Super-Jeans Cores

6Mairs et al. (2014)Starless SJ Cores are Rare

red = 50% tff green = 80% tff blue = 100 % tff

once sink forms, envelope accretes very rapidlyOffner et al. (2013): Rm6 simulation at 0.8 tff ; no feedback or magnetic fields

7Schnee et al. (2012); Crapsi et al. (2007)Starless SJ Cores are Not Fragmented?

Schnee et al. (2012) SMA/CARMA study of 5 starless SJ cores

4 non-detections consistent with starless core models

no fragments seen either: ALMA?

Models + CASA8

SJ Cores need better characterization More examples Better mass estimates (Tdust + ) Gas temperatures Kinematic studies Insights into other support mechanisms (turbulence + B)We need:

GBTHerschelJCMT9Locate, probe and glean new information on cores and super-Jeans cores in particular.More Examples: JCMT GBS

SCUBA-2 mapping of nearby SF clouds: Gould Belt Survey

covers 24 deg2 of high AV areas at 850 m to 1 3 mJy beam-1

due to spatial filtering, maps reveal compact structures (100s of cores and filaments)Image by R. Friesen; Hatchell et al. (2014, in prep)W40Serpens SouthAquila RiftSCUBA-2 850 m10JCMT Gould Belt Survey should reveal hundreds of cores in nearby clouds. Project is ~75% complete, project expected to end perhaps this winter.More Examples: JCMT GBS

OphiuchusL1689L1688Image by R. Friesen; Pattle et al. (2014, in prep)SCUBA-2 850 m11

More Examples: JCMT GBSS. Mairs et al. (2014, in prep)Orion A SouthSCUBA-2 850 m5 sigma contourislands12

fragmentsMore Examples: JCMT GBSS. Mairs et al. (2014, in prep)islandsZoom-in of Orion A South at 850 mNot stamp collecting - beyond just source extraction. We have large scale and small scale and we want to find unique and creative measures which link the two using GBS dataMore Examples: JCMT GBSS. Mairs et al. (2014, in prep)

Density = Molecular hydrogen, assumed a sphere - At this specific radius how dense would we have to be to become unstable assuming thermal support onlyProtostar catalogue - which of the ones we calculate to be collapsing are actually beyond that line - can tell us about additional support mechanisms we should investigate like B fields - perhaps different regions have different properties- it allows us to delve into physicsBetter Mass Estimates: JCMT

Perseus-NGC 1333Image by R. Friesen; Chen et al. (2014, in prep)SCUBA-2 850 mDSS2-infrared15Better Tdust & : JCMT + HerschelSadavoy et al. (2013)

Herschel Bands SCUBA-2 850 m band Different values of can fit Herschel data well SCUBA-2 data can be used to constrain (+ Tdust) = o(/o) ; o = 0.1 cm2 g-1 at 1000 GHz(Hillenbrand 1983)

= 1.5, 2.0, 2.5

Better Mass Estimates: JCMT16Better Tdust & : JCMT + Herschel

Combine spatially filtered Herschel data + SCUBA-2 data to determine + Tdust of compact structuresSadavoy et al. (2013)Filtered 250 m dataResidual 250 m dataPerseus B117Better Tdust & : JCMT + Herschel

Chen et al. (2014, in prep)Perseus - NGC 133318

Better Tdust & : JCMT + HerschelChen et al. (2014, in prep) what about o?? Perseus - NGC 133319

Line Studies of SJ CoresFriesen et al. (2019)NH3 : ncr ~ 104 cm-3 traces continuum hyperfine structure -> low optical depth gas temperatures NT/cs -> coherence? kinematics

Oph B clumpsNH3 (1,1) GBT+ VLA KFPA + VEGASnow available at GBT!20Gas Temperatures (line-of-sight)Chitsazzadeh et al. (2014, in prep)

Chitsazzadeh et al. : examining isolated cores on the verge of collapse with GBT

los ~ 9.5 0.6 K

NT/cs ~ 0.25 0.9 ; internal velocities dominated by thermal motionsL429-EL1521FL694-2L1517BL42921

Gas Temperatures (3D models) combined GBT + JVLA data of L694-2 & L1521F used NH3-derived (los) Tk and continuum data to fit column density structure and with B-E sphere used MOLLIE (Keto & Rybicki 2010) to model NH3L1521FL694-2Chitsazzadeh et al. (2014, in prep)22Gas Temperatures (3D models)Chitsazzadeh et al. (2014, in prep)

23Gas Kinematics: L1689-SMM16

Ophiuchus (L1689-S)SMM16 NH3-derived (los) temperatures, continuum data + BE sphere fit: (M/MJ) = 4.7/1.6 M = 3.4 no Spitzer or Herschel 70 m

Chitsazzadeh et al. (2014, in press)SCUBA 850 m24Gas Kinematics: L1689-SMM16

asymmetrically red HNC and HCN profiles: expansion of outer layers evenly spaced maxima and minima of V(thickthin): oscillations?

collapse not uniform?Chitsazzadeh et al. (2014, in press)Hill5 fits 25Summary The Jeans Mass provides a benchmark for identifying starless cores on the verge of collapse [Filtered?] continuum surveys are best way for locating more super-Jeans core candidates JCMT + Herschel data yield better core mass estimates, improving super-Jeans identification NH3 line observations reveal internal support, temperature profiles Other lines (HCN) can probe contraction: super-Jeans core contraction -> oscillations? New instruments = new probes of internal super- Jeans core structure and evolution 26