J/ApJ/760/147 13CO cores in the Taurus molecular cloud (Qian+, 2012)
13CO cores in the Taurus molecular cloud.
Qian L., Li D., Goldsmith P.F.
<Astrophys. J., 760, 147 (2012)>
=2012ApJ...760..147Q 2012ApJ...760..147Q (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Interstellar medium ; Carbon monoxide
Keywords: ISM: clouds - ISM: individual: Taurus - ISM: molecules - turbulence
Abstract:
Young stars form in molecular cores, which are dense condensations
within molecular clouds. We have searched for molecular cores traced
by 13CO J=1-->0 emission in the Taurus molecular cloud and
studied their properties. Our data set has a spatial dynamic range
(the ratio of linear map size to the pixel size) of about 1000 and
spectrally resolved velocity information, which together allow a
systematic examination of the distribution and dynamic state of 13CO
cores in a large contiguous region. We use empirical fit to the CO and
CO2 ice to correct for depletion of gas-phase CO. The 13CO core
mass function (13CO CMF) can be fitted better with a log-normal
function than with a power-law function. We also extract cores and
calculate the 13CO CMF based on the integrated intensity of 13CO
and the CMF from Two Micron All Sky Survey. We demonstrate that core
blending exists, i.e., combined structures that are incoherent in
velocity but continuous in column density. The core velocity
dispersion (CVD), which is the variance of the core velocity
difference δv, exhibits a power-law behavior as a function of
the apparent separation L: CVD(km/s)∝L(pc)0.7. This is
similar to Larson's law for the velocity dispersion of the gas. The
peak velocities of 13CO cores do not deviate from the centroid
velocities of the ambient 12CO gas by more than half of the line
width. The low velocity dispersion among cores, the close similarity
between CVD and Larson's law, and the small separation between core
centroid velocities and the ambient gas all suggest that molecular
cores condense out of the diffuse gas without additional energy from
star formation or significant impact from converging flows.
Description:
In this work, we use 12CO and 13CO data in the form of a (x,y,v)
cube of the Taurus molecular cloud as observed with the 13.7m FCRAO
telescope (Narayanan et al. 2008ApJS..177..341N 2008ApJS..177..341N) and the Two Micron
All Sky Survey (2MASS) extinction map of the same region (Pineda et
al. 2009ApJ...699L.134P 2009ApJ...699L.134P). The 12CO and 13CO lines were observed
simultaneously between 2003 and 2005. The map is centered at ,
RA=04:32:44.6, DE=+24:25:13.08 (2000.0), with an area of ∼98deg2.
Objects:
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RA (2000) DE Designation(s)
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04 32 44.6 +24 25 13.08 Taurus = Taurus molecular cloud
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 66 765 Properties of the cores found in the 3D 13CO
data cube (from erratum, 2013, ApJ, 765, 161)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID Index identifier
6 I1 h RAh Hour of Right Ascension (J2000)
8- 9 I2 min RAm Minute of Right Ascension (J2000)
11- 14 F4.1 s RAs Second of Right Ascension (J2000)
16- 17 I2 deg DEd Degree of Declination (J2000)
19- 20 I2 arcmin DEm Arcminute of Declination (J2000)
22- 25 F4.1 arcsec DEs Arcsecond of Declination (J2000)
27- 29 F3.1 arcmin Rmaj Semi-major axis
31- 33 F3.1 arcmin Rmin Semi-minor axis
35- 39 F5.1 deg PA Position angle; angle from north to Rmaj
41- 44 F4.1 K TPeak Peak temperature
46- 49 F4.1 Msun M Mass
51- 55 F5.1 Msun MVir Virial mass
57- 59 F3.1 km/s FWHM Line Full-Width of Half-Maximum
61- 66 I6 cm-3 NH2 Estimated mean NH2 density
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Acknowledgements:
Lei Qian, lqian(at)nao.cas.cn
(End) Patricia Vannier [CDS] 28-Mar-2014