J/MNRAS/483/3022 Age gradients throughout the Galaxy with LPVs (Grady+, 2019)
Age gradients throughout the Galaxy with long-period variables.
Grady J., Belokurov V., Evans N.W.
<Mon. Not. R. Astron. Soc., 483, 3022-3035 (2019)>
=2019MNRAS.483.3022G 2019MNRAS.483.3022G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, giant ; Stars, distances ; Milky Way ;
Optical
Keywords: Galaxy: disc - Galaxy: halo - Galaxy: structure
Abstract:
We assemble the largest sample of oxygen-rich (O-rich) Miras and
associated long-period variables (LPVs) to date and highlight their
importance for age dating the components of the Galaxy. Using data
from the Catalina Surveys and the All Sky Automated Survey for
Supernovae, we extract a clean sample of ∼2200 O-rich LPVs, stretching
from the Galactic Bulge to the distant halo. We estimate ∼80 per cent
of our selected sample to be comprised of O-rich LPVs. Given that the
period of LPVs correlates with age, this offers a new way of
determining age gradients throughout the Galaxy. We use our sample to
show (i) disc O-rich LPVs have periods increasing on moving outwards
from ∼3 to 15kpc, so the outer disc LPVs are younger than the inner
disc, (ii) the transition from younger disc to halo LPVs occurs at r
∼15kpc and is marked by a plummeting in period, (iii) there exists a
population of young O-Miras likely kicked from the disc to heights of
order of |Z|∼10kpc, and (iv) great circle counts of old LPVs show
evidence for distant debris agglomeration associated with the
Magellanic Clouds. We spotlight the importance of Miras and LPVs in
the Era of Gaia as universal chronometers of the Galactic populations.
Description:
This work exploits data from two primary sources that of the Catalina
Surveys and the All Sky Automated Survey for Supernovae (ASAS-SN). The
Catalina Surveys catalogue is comprised of two main components
surveying the Northern (Drake et al. 2014ApJS..213....9D 2014ApJS..213....9D, Cat.
J/ApJS/213/9) and Southern (Drake et al. 2017MNRAS.469.3688D 2017MNRAS.469.3688D, Cat.
J/MNRAS/469/3688) sky, respectively. The surveys in both hemispheres
are analysed by the Catalina Real-Time Transient Survey (CRTS) in
search of optical transient phenomena. Data are extracted from both
subsets and will be referred to as CRTS hereon. Our sample of LPV
candidates is then cross-matched with the 2MASS catalogue (Skrutskie
et al. 2006AJ....131.1163S 2006AJ....131.1163S, Cat. VII/233) to obtain JHKs magnitudes,
yielding a total of 960 unique sources.
The ASAS-SN project is an all-sky optical survey with published
classifications of variable stars (Jayasinghe et al.
2018MNRAS.477.3145J 2018MNRAS.477.3145J, Cat. II/366). Cross-matching the ASAS-SN Mira
candidates with 2MASS provided 1831 sources for study. A cross-match
radius of 1arcsec was used in both instances. Magnitudes are
dereddened with extinction coefficients of RJ=0.72, RH=0.46, and
RKs=0.306 combined with the reddening values of Schlegel, Finkbeiner
& Davis (1998ApJ...500..525S 1998ApJ...500..525S).
The selection of our sample proceeds via the application of two main
cuts. The work of Yuan et al. (2017AJ....154..149Y 2017AJ....154..149Y, Cat. J/AJ/154/149)
and Glass et al. (1995MNRAS.273..383G 1995MNRAS.273..383G) shows that the colour indices
of Mira increase as a function of period, itself a proxy for age.
Glass et al. (1995MNRAS.273..383G 1995MNRAS.273..383G) provide linear colour-period
relations for O-Miras in the SAAO photometric system. For this work,
the J-H relation is converted into the 2MASS photometric system via
the transformation of Carpenter (2001AJ....121.2851C 2001AJ....121.2851C). Associated
errors of the original linear relations and colour transformations are
combined to produce a 1σ bound defining the selection cut for
O-Mira from our sample. We note that the photometric transformation of
Miras can be affected by broad absorption bands. We use the
colour-period relation of Yuan et al. (2017AJ....154..149Y 2017AJ....154..149Y, Cat.
J/AJ/154/149) purely as a guide for our selection and have checked
that the applied photometric transformation has no significant effect
on our results.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 124 481 Sample of the CRTS Mira and LPVs that pass our
selections
tablea2.dat 74 1741 Sample of the ASAS-SN that pass our selections
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 21 A21 --- Name Catalina Real Time Survey (CRTS) identifier
(CRTS JHHMMSS.s+DDMMSS)
23- 41 F19.15 deg RAdeg Right ascension (J2000)
43- 62 F20.16 deg DEdeg Declination (J2000)
64- 83 F20.17 mag AmpV Visual amplitude
85-102 F18.14 d Period Variability period
104-124 F21.17 kpc Dist Heliocentric distance derived from our
period-luminosity relation (G1)
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 20 F20.16 deg RAdeg Right ascension (J2000)
22- 41 F20.16 deg DEdeg Declination (J2000)
43- 46 F4.2 mag AmpV Visual amplitude
48- 52 F5.1 d Period Variability period
54- 74 F21.17 kpc Dist Heliocentric distance derived from our
period-luminosity relation (G1)
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Global Notes:
Note (G1): The heliocentric distances are estimated with the equation:
MKs=-6.90-3.77(logP-2.3)-2.23(logP-2.3)2-0.17, where P is the
period in days and MKs is the absolute magnitude in the Ks band.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 22-Jul-2022