J/A+A/665/A82 ALMA data cubes for OH/IR stars (Olofsson+, 2022)
CO line observations of OH/IR stars in the inner Galactic Bulge:
Characteristics of stars at the tip of the AGB.
Olofsson H., Khouri T., Sargent B.A., Winnberg A., Blommaert J.A.D.L.,
Groenewegen M.A.T., Muller S., Kastner J.H., Meixner M., Otsuka M.,
Patel N., Ryde N., Srinivasan S.
<Astron. Astrophys. 665, A82 (2022)>
=2022A&A...665A..82O 2022A&A...665A..82O (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Infrared sources ; Radio lines ; Carbon monoxide
Keywords: AGB and post-AGB - circumstellar matter - stars: mass loss -
radio lines: stars
Abstract:
OH/IR stars are examples of late stellar evolution on the asymptotic
giant branch (AGB), and they are, as such, important objects to study.
They are also excellent probes of stellar populations, in particular
in regions of high interstellar extinction such as the central regions
of our Galaxy.
Our goal is to characterise the stellar and circumstellar properties
of high-mass-loss-rate OH/IR stars in the inner Galactic Bulge using
the Atacama Large Millimeter/submillimeter Interferometer (ALMA).
Rotational lines of 12CO and 13CO, as well as a millimetre-wave
continuum, have been observed for a sample of 22 OH/IR stars in
directions within 2° of the Galactic Centre. Photometry data
(∼1-30um) have been gathered from the literature to construct spectral
energy distributions (SEDs) and to determine pulsational variability.
Radiative transfer models have been used to interpret the line and
photometry data.
All stars in the sample were detected in at least one CO line, and
eight objects were detected in 324GHz continuum. Based on luminosity
criteria, the sample is divided into 17 objects that most likely lie
within the inner Galactic Bulge, and five objects that are most likely
foreground objects. The median luminosity of the inner-Galactic-Bulge
sub-sample, 5600L☉, corresponds to an initial mass in the range
1.2-1.6M☉, indicating that these inner-Galactic-Bulge OH/IR
stars descend from solar-type stars. The objects in this sub-sample
are further divided into two classes based on their SED
characteristics: Eleven objects have SEDs that are well matched by
models invoking dust envelopes extending from a few stellar radii and
outwards, while six objects are better modelled as having detached
dust envelopes with inner radii in the range 200-600au and warmer
central stars. The former objects have periodic variability, while the
latter objects are predominantly non-periodic. The median
gas-mass-loss rate, gas terminal expansion velocity, gas-to-dust mass
ratio, and circumstellar 12CO/13CO abundance ratio have been
estimated to be 2x10-5M☉/yr, 18km/s, 200 (excluding the
sources with detached dust envelopes, which show markedly lower
gas-to-dust ratios), and 5, respectively, for the inner-Galactic-Bulge
sub-sample. All line brightness distributions are resolved at an
angular scale of ∼0.15", but only two objects show a structure in
their circumstellar envelopes at our resolution and sensitivity. In
both cases, this structure takes the form of a cavity and a bipolar
morphology.
The inner-Galactic-Bulge sub-sample consists of high mass-loss-rate
stars that descend from solar-type progenitors and that lie near the
tip of the AGB. Some of the sample stars may have recently ceased mass
loss and, hence, have begun to evolve beyond the AGB, as evidenced by
a change in circumstellar characteristics and indications of warmer
central stars. The inferred very low stellar 12C/13C isotope
ratios are indicative of CNO-cycle nuclear processing, and they are
most likely established at the surfaces of the stars during the first
dredge-up on the red giant branch since these stars are not expected
to experience hot-bottom burning. The inner-Galactic-Bulge OH/IR stars
studied here constitute an excellent sample of equidistant objects for
the purpose of understanding the evolution of the mass-loss-rate
characteristics at the tip of the AGB.
Description:
ALMA data cubes in fits-format for 22 sources. For each source there
are 3 fits files containing the 12CO(2-1), 12CO(3-2), and
13CO(3-2) line data, and 3 fits files containing the 222, 324, and
339GHz continuum data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 38 22 List of sources
photom.dat 160 309 Photometry data used to construct the spectral
energy distributions for 22 sources
list.dat 139 132 List of fits images and datacubes
fits/* . 132 Individual fits images and datacubes
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Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1 A1 --- ID [a-v] Identification letter
4- 18 A15 --- Name Source Name
20- 28 F9.5 deg RAdeg Right Ascension of center (J2000)
30- 38 F9.5 deg DEdeg Declination of center (J2000)
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Byte-by-byte Description of file: photom.dat
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Bytes Format Units Label Explanations
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1 A1 --- ID [a-v] Identification letter
4- 18 A15 --- Name Source Name
20 A1 --- u_lambda [#]
21- 28 F8.3 um lambda Effective centre wavelength of the photometry
32- 38 E7.3 Jy S Flux density
41- 47 E7.3 Jy e_S ? Uncertainty of the flux density estimate (1)
49- 55 F7.4 Jy Scorr ? Extinction-corrected flux density (2)
57-122 A66 --- Inst/Cat Instrument/Catalogue from which the data
were taken (3)
123-160 A38 --- Com Comments
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Note (1): Only for foreground sources (b, c and f)
Note (2): Only for inner-Galactic-Bulge sources (all except b, c and f)
Note (3): References are:
Abrahamyan+2015 = Abrahamyan et al., 2015, Cat. II/338
Chambers+2016 = Chambers et al., 2016, Cat. II/349
Cutri+2013 = Cutri et al., 2013, Cat. II/328
Egan+2003 = Egan et al., 2003, Cat. V/114
Elia+2017 = Elia et al., 2017MNRAS.471..100E 2017MNRAS.471..100E, Cat. J/MNRAS/471/100
Gutermuth+2015 = Gutermuth & Heyer, 2015AJ....149...64G 2015AJ....149...64G, Cat. J/AJ/149/54
Hinz+2009 = Hinz et al., 2009ApJS..181..227H 2009ApJS..181..227H, Cat. J/ApJS/181/227
IPAC 2008 = IPAC, 2008, Cat. II/293/
ISAS/JAXA, 2010 = ISAS/JAXA, 2010. Cat. II/297
Lucas+2012 = Lucas et al., =2008MNRAS.391..136L 2008MNRAS.391..136L, Cat. II/316
Molinari+2016 = Molinari et al., 2016A&A...591A.149M 2016A&A...591A.149M, Cat. J/A+A/588/75
Omont+2003 = Omont et al., 2003A&A...403..975O 2003A&A...403..975O, Cat. II/243
Sevenster+2002 = Sevenster et al., 2002AJ....123.2772S 2002AJ....123.2772S, Cat. J/AJ/123/2772
Zacharias+2005 = Zacharias et al., 2005, Cat. I/297
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 29 I2 --- Nz ? Number of slice for the datacube
31- 56 A26 "datime" Obs.date Observation date
58- 64 F7.3 GHz bFreq Frequency or lower value of frequency interval
66- 72 F7.3 GHz BFreq ? Upper value of frequency interval
74- 80 F7.5 MHz dFreq ? Frequency resolution
82- 86 I5 Kibyte size Size of FITS file
88- 99 A12 --- FileName Name of FITS file, in subdirectory fits
101-139 A39 --- Title Title of the FITS file
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Acknowledgements:
Hans Olofsson, hans.olofsson(at)chalmers.se
(End) Patricia Vannier [CDS] 27-Jul-2022