J/A+A/682/A149 Herbig disks gas mass using CO isotopologues (Stapper+, 2024)
Constraining the gas mass of Herbig disks using CO isotopologues.
Stapper L.M., Hogerheijde M.R., van Dishoeck E.F., Lin L., Ahmadi A.,
Booth A.S., Grant S.L., Immer K., Leemker M., Perez-Sanchez A.F.
<Astron. Astrophys. 682, A149 (2024)>
=2024A&A...682A.149S 2024A&A...682A.149S (SIMBAD/NED BibCode)
ADC_Keywords: Carbon monoxide ; Models ; Radio lines ; Stars, early-type ;
YSOs ; Models
Keywords: surveys - protoplanetary disks - stars: early-type -
stars: pre-main sequence - stars: variables: T Tauri, Herbig Ae/Be -
submillimeter: planetary systems
Abstract:
The total disk mass sets the formation potential for exoplanets.
Obtaining the disk mass is however not an easy feat, as one needs to
consider the optical thickness, temperature, photodissociation, and
freeze-out of potential mass tracers. Carbon-monoxide (CO) has been
used as a gas mass tracer in T Tauri disks, but was found to be less
abundant than expected due to the freeze-out and chemical conversion
of CO on the surfaces of cold dust grains. The disks around more
massive intermediate mass pre-main sequence stars called Herbig disks
are likely to be warmer, allowing for the possibility of using CO as a
more effective total gas mass tracer.
This work aims to obtain the gas mass and size of Herbig disks
observed with ALMA and compare these to previous works on T Tauri
disks and debris disks.
Using ALMA archival data and new NOEMA data of 12CO, 13CO, and
C18O transitions of 35 Herbig disks within 450 pc, the masses were
determined using the thermo-chemical code Dust And LInes (DALI). A
grid of models was run spanning five orders of magnitude in disk mass,
for which the model CO line luminosities could be linked to the
observed luminosities. Survival analysis was used to obtain cumulative
distributions of the resulting disk masses. These were compared with
dust masses from previous work to obtain gas-to-dust ratios for each
disk. In addition, radii for all three isotopologues were obtained.
The majority of Herbig disks for which 13CO and C18O were detected
are optically thick in both. For these disks, the line flux
essentially only traces the disk size and only lower limits to the
mass can be obtained. Computing the gas mass using a simple optically
thin relation between line flux and column density results in an
underestimate of the gas mass of at least an order of magnitude
compared to the masses obtained with DALI. The inferred gas masses
with DALI are consistent with a gas-to-dust ratio of at least 100.
These gas-to-dust ratios are two orders of magnitude higher compared
to those found for T Tauri disks using similar techniques, even over
multiple orders of magnitude in dust mass, illustrating the importance
of the chemical conversion of CO in colder T Tauri disks. Similar high
gas-to-dust ratios are found for Herbig group I and II disks. Since
group II disks have dust masses comparable to T Tauri disks, their
higher CO gas masses illustrate the determining role of temperature.
Compared to debris disks, Herbig disks have gas masses higher by four
orders of magnitude. At least one Herbig disk, HD 163296, has a
detected molecular disk wind, but our investigation has not turned up
other detections of the CO disk wind in spite of similar
sensitivities.
Herbig disks are consistent with a gas-to-dust ratio of at least 100
over multiple orders of magnitude in dust mass. This indicates a
fundamental difference between CO emission from Herbig disks and T
Tauri disks, which is likely linked to the warmer temperature of the
Herbig disks.
Description:
The resulting integrated CO luminosities and radii from our model grid
run with the thermochemical code DALI. Each line is a different model.
The luminosities and radii are given for 12CO, 13CO, C18O,
C17O, 13C18O, and 13C17O for the J=2-1 and J=3-2
transitions. Additionally, for each model the specific parameters are
given as well. All models were raytraced at a distance of 100pc.
Hence, the luminosities given are 4pi*1002 times the integrated flux
over the disk in Jy.km/s. The given radius is the radius at which 90%
of the total disk integrated flux is surrounded.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
models.dat 574 10800 The luminosities and radii extracted from the
models and the model parameters
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Byte-by-byte Description of file: models.dat
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Bytes Format Units Label Explanations
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1- 4 F4.1 [Msun] logMgas The tenth logarithm of the gas mass
6- 9 F4.1 Lsun Lstar Stellar luminosity
11- 13 F3.1 --- gamma Surface density profile power law index
15- 17 F3.1 --- psi Flaring index vertical distribution
19- 22 F4.2 rad hc Scale height at distance Rc
24- 28 F5.1 AU Rc Critical radius surface density profile
30- 33 F4.1 deg inc Inclination of the disk
35- 60 F26.16 Jy.km/s/pc2 L12COJ21 Luminosity of the 12CO J=2-1 line
62- 81 F20.15 AU R12COJ21 90% radius of the 12CO J=2-1 line
83-108 F26.16 Jy.km/s/pc2 L12COJ32 Luminosity of the 12CO J=3-2 line
110-129 F20.15 AU R12COJ32 90% radius of the 12CO J=3-2 line
131-155 F25.16 Jy.km/s/pc2 L13COJ21 Luminosity of the 13CO J=2-1 line
157-176 F20.15 AU R13COJ21 90% radius of the 13CO J=2-1 line
178-203 F26.16 Jy.km/s/pc2 L13COJ32 Luminosity of the 13CO J=3-2 line
205-224 F20.15 AU R13COJ32 90% radius of the 13CO J=3-2 line
226-248 E23.17 Jy.km/s/pc2 LC18OJ21 Luminosity of the C18O J=2-1 line
250-269 F20.15 AU RC18OJ21 90% radius of the C18O J=2-1 line
271-291 E21.15 Jy.km/s/pc2 LC18OJ32 Luminosity of the C18O J=3-2 line
293-312 F20.15 AU RC18OJ32 90% radius of the C18O J=3-2 line
314-337 F24.16 Jy.km/s/pc2 LC17OJ21 Luminosity of the C17O J=2-1 line
339-357 F19.15 AU RC17OJ21 90% radius of the C17O J=2-1 line
359-380 E22.16 Jy.km/s/pc2 LC17OJ32 Luminosity of the C17O J=3-2 line
382-400 F19.15 AU RC17OJ32 90% radius of the C17O J=3-2 line
402-424 E23.17 Jy.km/s/pc2 L13C18OJ21 Luminosity of the 13C18O J=2-1 line
426-445 F20.15 AU R13C18OJ21 90% radius of the 13C18O J=2-1 line
447-468 E22.16 Jy.km/s/pc2 L13C18OJ32 Luminosity of the 13C18O J=3-2 line
470-488 F19.15 AU R13C18OJ32 90% radius of the 13C18O J=3-2 line
490-511 E22.16 Jy.km/s/pc2 L13C17OJ21 Luminosity of the 13C17O J=2-1 line
513-532 F20.15 AU R13C17OJ21 90% radius of the 13C17O J=2-1 line
534-554 E21.15 Jy.km/s/pc2 L13C17OJ32 Luminosity of the 13C17O J=3-2 line
556-574 F19.15 AU R13C17OJ32 90% radius of the 13C17O J=3-2 line
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Acknowledgements:
Lucas Stapper, stapper(at)strw.leidenuniv.nl
(End) Lucas Stapper [Leiden Observatory], Patricia Vannier [CDS] 18-Dec-2023