J/PASJ/73/487 C18O cores in Orion A (Takemura+, 2021)
The C18O core mass function toward Orion A: Single-dish observations.
Takemura H., Nakamura F., Ishii S., Shimajiri Y., Sanhueza P.,
Tsukagoshi T., Kawabe R., Hirota T., Kataoka A.
<Publ. Astron. Soc. Jap., 73, 487-503 (2021)>
=2021PASJ...73..487T 2021PASJ...73..487T (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Interstellar medium ; Morphology
Keywords: stars: formation - ISM: clouds - ISM: molecules
Abstract:
We have performed an unbiased dense core survey toward the Orion A
Giant Molecular Cloud in the C18O (J=1-0) emission line taken with
the Nobeyama Radio Observatory (NRO) 45 m telescope. The effective
angular resolution of the map is 26", which corresponds to ∼0.05pc at
a distance of 414pc. By using the Herschel-Planck H2 column
density map, we calculate the C18O fractional abundance and find
that it is roughly constant over the column density range of
≲5x1022cm-3, although a trend of C18O depletion is determined
toward higher column density. Therefore, C18O intensity can follow
the cloud structure reasonably well. The mean C18O abundance in
Orion A is estimated to be 5.7x10-7, which is about three times
larger than the fiducial value. We identified 746 C18O cores with
astrodendro and classified 709 cores as starless cores. We compute the
core masses by decomposing the Herschel-Planck dust column density
using the relative proportions of the C18O integrated intensities of
line-of-sight components. Applying this procedure, we attempt to
remove the contribution of the background emission, i.e., the ambient
gas outside the cores. Then, we derived mass function for starless
cores and found that it resembles the stellar initial mass function
(IMF). The CMF for starless cores, dN/dM, is fitted with a power-law
relation of Mα with a power index of α=-2.25±0.16 at
the high-mass slope (≳0.44M☉). We also found that the ratio of
each core mass to the total mass integrated along the line of sight is
significantly large. Therefore, in the previous studies, the core
masses derived from the dust image are likely to be overestimated by
at least a factor of a few. Accordingly, such previous studies may
underestimate the star formation efficiency of individual cores.
Description:
We carried out on-the-fly (OTF) mapping observations of C18O (J=1-0,
109.782182GHz) toward Orion A using the FOREST receivers mounted on
the NRO 45 m telescope. the observations were done in the period from
2016 March to 2017 March.
We identified 709 starless cores and 37 protostellar cores.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 64 746 Properties of identified cores
table4.dat 46 746 Properties of identified cores
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See also:
J/ApJ/665/1194 : Dense cores in the Orion A cloud survey (Ikeda+, 2007)
J/ApJ/846/144 : Virial analysis of the dense cores in Orion A (Kirk+, 2017)
J/ApJS/217/7 : Orion A dense cores based on 1.1mm and C18O
(Shimajiri+, 2015)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/746] Sequential number
5 I1 h RAh Right ascension (J2000)
7- 8 I2 min RAm Right ascension (J2000)
10- 13 F4.1 s RAs [] Right ascension (J2000)
15 A1 --- DE- Declination sign (J2000)
16 I1 deg DEd Declination (J2000)
18- 19 I2 arcmin DEm Declination (J2000)
21- 22 I2 arcsec DEs [] Declination (J2000)
24- 27 F4.1 km/s vLSR LSR velocity
29- 33 I5 arcsec2 Area Exact area of the core projected on to
the plane of the sky
35- 37 I3 arcsec 2Rcore Angular core diameter
39- 42 F4.2 pc 2Rcorepc Linear core diameter
44- 47 F4.1 arcsec amajor Semi-major axis
49- 52 F4.1 arcsec aminor Semi-minor axis
54- 57 I4 deg PA [] Position angle
59- 62 F4.2 km/s dVcore FWHM velocity width
64 A1 --- YSO [Y/N] YSO ?
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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- 3 I3 --- ID [1/746] Sequential number
5- 7 F3.1 K Tpeakmb Peak temperature
9- 15 F7.1 K Ttotalmb Total temperature
17- 20 F4.1 Msun Mcore Core mass
22- 25 F4.1 --- Mvir/Mcore Virial ratio, Mvir/Mcore
27- 30 F4.1 10+4cm-2 n Mean number density
32- 36 F5.1 K Tex Mean excitation temperature
38- 41 F4.1 10+15cm-2 NC18O Mean column density of C18O
43- 46 F4.1 10-7 XC18O Mean fractional abundance of C18O
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History:
From electronic version of the journal
References:
Takemura et al. Paper I. 2021ApJ...910L...6T 2021ApJ...910L...6T
Takemura et al. Paper II. 2021PASJ...73..487T 2021PASJ...73..487T This catalog
Takemura et al. 2023ApJS..264...35T 2023ApJS..264...35T Cat. J/ApJS/264/35
(End) Patricia Vannier [CDS] 19-Aug-2021