J/MNRAS/483/407 LMT/AzTEC 1.1mm Survey of Mon R2 dense cores (Sokol+, 2019)
Early science with the Large Millimetre Telescope: An LMT/AzTEC 1.1 mm Survey
of dense cores in the Monoceros R2 giant molecular cloud.
Sokol A.D., Gutermuth R.A., Pokhrel R., Gomez-Ruiz A.I., Wilson G.W.,
Offner S.S.R., Heyer M., Luna A., Schloerb F.P., Sanchez D.
<Mon. Not. R. Astron. Soc., 483, 407-424 (2019)>
=2019MNRAS.483..407S 2019MNRAS.483..407S (SIMBAD/NED BibCode)
ADC_Keywords: Star Forming Region ; Protostars ; Interstellar medium ;
Molecular clouds ; Millimetric/submm sources
Keywords: stars: formation - stars: protostars - ISM: general
Abstract:
We present a 1.1mm census of dense cores in the Mon R2 giant molecular
cloud with the AzTEC instrument on the Large Millimetre Telescope. We
detect 295 cores (209 starless and 86 with protostars) in a two square
degree shallow survey. We also carry out a deep follow-up survey of
nine regions with low to intermediate (3<AV<7) gas column densities
and detect 60 new cores in the deeper survey that allows us to derive
a completeness limit. After performing corrections for low
signal-to-noise cores, we find a median core mass of ∼2.1M☉ and
a median size of 0.08pc. 46 per cent of the cores (141) have masses
exceeding the local Bonnor-Ebert mass for cores with T=12K, suggesting
that in the absence of supporting non-thermal pressure, these regions
are unstable to gravitational collapse. We present the core mass
function (CMF) for various subdivisions of the core sample. We find
that cores with masses >10M☉ are exclusively found in regions
with high core number densities and that the CMF of the starless cores
has an excess of low-mass cores (<5M☉) compared to the CMF of
protostellar cores. We report a power-law correlation of index
1.99±0.03 between local core mass density and gas column density (as
traced by Herschel) over a wide range of size scales (0.3-5pc). This
power law is consistent with that predicted for thermal fragmentation
of a self-gravitating sheet. Finally, we find the global core
formation efficiency increases with gas column density, reaching ∼43
per cent efficiency for gas with AV≥30.
Description:
We observed Mon R2 with AzTEC (Wilson et al. 2008MNRAS.386..807W 2008MNRAS.386..807W), the
144-element 1.1mm bolometer array on the 50-m diameter Large
Millimetre Telescope Alfonso Serrano (LMT) in its 32m diameter early
science configuration from 2014 November 27 to 2015 January 31.
Fourteen fields totaling ∼2deg2 were chosen based on the Herschel
survey of the entire cloud (Pokhrel et al. 2016MNRAS.461...22P 2016MNRAS.461...22P) such
that we covered the majority of the cloud area found at
N(H2)>3x1021cm-2 along with adjacent, lower column density
areas within our rectangular survey areas. In addition to the large
area shallow survey, we obtained a deeper LMT/AzTEC 1.1mm survey of
selected fields in Mon R2 from 2016 January 22 to 2016 February 25
with the goal of characterizing the low-mass end of the CMF with
higher confidence. We selected nine regions, each 5arcmin in diameter,
that had relatively low mean column density but exhibited filamentary
structure in the Herschel map (Pokhrel et al. 2016MNRAS.461...22P 2016MNRAS.461...22P) and
had relatively few dense cores detected in our shallow survey.
The primary goal of this survey is to provide the first ever census of
dense gas cores in the Mon R2 GMC. We adopt a core identification
process that is similar to the classic two-dimensional (2D) Clumpfind
algorithm (Williams, de Geus & Blitz 1994ApJ...428..693W 1994ApJ...428..693W, Cat.
J/ApJ/428/693).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 106 295 All core properties
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/295] Core ID
5- 6 I2 h RAh Right ascension (J2000)
8- 9 I2 min RAm Right ascension (J2000)
11- 14 F4.1 s RAs Right ascension (J2000)
16 A1 --- DE- Declination sign (J2000)
17- 18 I2 deg DEd Declination (J2000)
20- 21 I2 arcmin DEm Declination (J2000)
23- 26 F4.1 arcsec DEs Declination (J2000)
28- 33 F6.1 arcsec2 Area Total footprint area
35- 40 F6.1 mJy TotFlux Total flux at 1.1mm in the footprint
42- 47 F6.1 mJy CorrFlux Corrected total flux at 1.1mm (1)
49- 51 F3.1 --- CF/TF Corrected total flux to total flux at 1.1mm
ratio
53- 59 F7.3 --- S/N Total flux signal to noise ratio
61 A1 --- Protostar [Y,N] Indicates if there is a protostar in the
core
63- 68 F6.1 arcsec2 HPPA Half-peak-power (HPP) area
70- 75 F6.1 arcsec2 CorrHPPA Corrected HPPA (2)
77- 82 F6.1 Jy/beam PeakFlux Peak flux at 1.1mm per beam
84- 87 F4.1 Msun CorrMass Corrected core mass
89- 92 F4.2 pc CorrFWHM Corrected full width at half-maximum (FWHM)
94-100 F7.3 --- PSN Peak signal to noise ratio
102-106 F5.3 --- Prob Confidence score (3)
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Note (1): The corrected flux is computed using the equation:
Fcorr=Fpeak/[Fpeak/Ftot-δR], where δR=5.25x(S/N)-1.8
Note (2): The corrected HPPA area is computed using the equation:
log(CorrHPPA)=-0.9228xlog(Fpeak/Ftot-δR)-1.432, with HPPA in
arcmin2.
Note (3): For every observed core candidate, we assign a confidence score based
on the ratio of the 2D histogram bins observed over normalized noise
at that position. All observed cores with less than a 25 per cent
chance of being consistent with a false detection are used for our
final core selection, yielding a total of 295 cores.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 06-Jul-2022