J/ApJ/788/59 Parametric model for circumstellar disks gas mass (Williams+, 2014)
A parametric modeling approach to measuring the gas masses of circumstellar
disks.
Williams J.P., Best W.M.J.
<Astrophys. J., 788, 59 (2014)>
=2014ApJ...788...59W 2014ApJ...788...59W (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Stars, masses ; Effective temperatures
Keywords: circumstellar matter - planets and satellites: formation -
protoplanetary disks
Abstract:
The disks that surround young stars are mostly composed of molecular
gas, which is harder to detect and interpret than the accompanying
dust. Disk mass measurements have therefore relied on large and
uncertain extrapolations from the dust to the gas. We have developed a
grid of models to study the dependencies of isotopologue CO line
strengths on disk structure and temperature parameters and find that a
combination of 13CO and C18O observations provides a robust
measure of the gas mass. We apply this technique to Submillimeter
Array observations of nine circumstellar disks and published
measurements of six well studied disks. We find evidence for selective
photodissociation of C18O and determine masses to within a factor of
about three. The inferred masses for the nine disks in our survey
range from 0.7 to 6 MJup, and all are well below the extrapolation
from the interstellar medium gas-to-dust ratio of 100. This is
consistent with the low masses of planets found around such stars, and
may be due to accretion or photoevaporation of a dust-poor upper
atmosphere. However, the masses may be underestimated if there are
more efficient CO depletion pathways than those known in molecular
clouds and cold cores.
Description:
Circumstellar disks are relatively small, faint objects that have, to
date, required long integrations with millimeter wavelength
interferometers to study their molecular gas content. Consequently,
only a small number of disks have been imaged in isotopologue lines
and most analyses have been tailored to the individual object. Driven
by the moderately large sample size but low signal-to-noise level in
our data here, we use a different approach. Rather than analyze each
disk individually, we create a large grid of models that span a wide
range of disk parameters, particularly in gas mass, and compare with
the data in a uniform way.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 131 18144 Parametric Model Output
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See also:
J/ApJ/784/62 : Circumstellar disks around binary stars in Taurus
(Akeson+, 2014)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 F3.1 Msun M* Stellar mass (0.5, 1.0)
5- 10 F6.4 Msun Mgas Gas mass (0.0001, 0.0003, 0.0010, 0.0030,
0.0100, 0.0300, 0.1000)
12- 14 F3.1 --- gamma Surface density power law index (0.0, 0.8, 1.5)
16- 18 I3 AU Rc Characteristic disk radius (30, 60, 100, 200)
20- 22 I3 K Tmid1 Inner midplane temperature (100, 200, 300)
24- 27 I4 K Tatm1 Inner atmopsheric temperature
(500, 750, 1000, 1500)
29- 32 F4.2 --- q Radial power law index (0.45, 0.55, 0.65)
34- 35 I2 deg Inc Inclination (0, 45, 90)
37- 41 F5.3 --- ffreeze Mass fraction where CO is frozen out
43- 47 F5.3 --- fdissoc Mass fraction where CO is dissociated
49- 54 F6.3 Jy.km/s FCO10 Integrated intensity of CO J=1-0 line
56- 62 F7.3 Jy.km/s FCO21 Integrated intensity of CO J=2-1 line
64- 70 F7.3 Jy.km/s FCO32 Integrated intensity of CO J=3-2 line
72- 76 F5.3 Jy.km/s F13CO10 Integrated intensity of 13CO J=1-0 line
78- 83 F6.3 Jy.km/s F13CO21 Integrated intensity of 13CO J=2-1 line
85- 91 F7.3 Jy.km/s F13CO32 Integrated intensity of 13CO J=3-2 line
93- 97 F5.3 Jy.km/s FC18O10 Integrated intensity of C18O J=1-0 line
99-104 F6.3 Jy.km/s FC18O21 Integrated intensity of C18O J=2-1 line
106-111 F6.3 Jy.km/s FC18O32 Integrated intensity of C18O J=3-2 line
113-117 F5.3 Jy.km/s FC18O10l Integrated intensity limit of low
abundance C18O J=1-0 line
119-124 F6.3 Jy.km/s FC18O21l Integrated intensity limit of low
abundance C18O J=2-1 line
126-131 F6.3 Jy.km/s FC18O32l Integrated intensity limit of low
abundance C18O J=3-2 line
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 06-Jul-2017