J/MNRAS/455/2216 Outer bulge O-rich Mira's JHKL photometry (Catchpole+, 2016)
The age and structure of the Galactic Bulge from Mira variables.
Catchpole R.M., Whitelock P.A., Feast M.W., Hughes S.M.G., Irwin M.,
Alard C.
<Mon. Not. R. Astron. Soc. 455, 2216 (2016)>
=2016MNRAS.455.2216C 2016MNRAS.455.2216C (SIMBAD/NED BibCode)
ADC_Keywords: Galactic plane ; Stars, late-type ; Stars, variable ;
Photometry, infrared
Keywords: stars: AGB and post AGB - stars: variables - Galaxy: bulge -
Galaxy: structure - infrared: stars
Abstract:
We report periods and JHKL observations for 643 oxygen-rich Mira
variables found in two outer bulge fields at b=-7° and l=±8°
and combine these with data on 8057 inner bulge Miras from the OGLE,
Macho and 2MASS surveys, which are concentrated closer to the Galactic
centre. Distance moduli are estimated for all these stars. Evidence is
given showing that the bulge structure is a function of age. The
longer period Miras (LogP>2.6, age∼5Gyr and younger) show clear
evidence of a bar structure inclined to the line of sight in both the
inner and outer regions. The distribution of the shorter period
(metal-rich globular cluster age) Miras, appears spheroidal in the
outer bulge. In the inner region these old stars are also distributed
differently from the younger ones and possibly suggest a more complex
structure.
These data suggest a distance to the galactic centre R0, of 8.9kpc,
with an estimated uncertainty of ∼0.4kpc. The possible effect of
helium enrichment on our conclusions is discussed.
Description:
JHKL photometry in the SAAO system, is presented for 643 stars
identified as Mira variables. The candidate stars were found and their
periods determined, over a period of 6 years on AAO Schmidt, using
IVN (I band) photographic plates.
Most of the stars have only two observations, which are averaged. The
errors of observation are 0.03 in JHK and 0.05 in L.
All the Miras have been identified with 2MASS (equinox 2000) objects
and their 2MASS positions are given.
The visual interstellar extinction, deduced for each Mira, using the
Whitelock method (see paper) is also listed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 71 643 Mira positions and JHKL magnitudes
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right ascension (J2000.0)
12- 21 F10.6 deg DEdeg Declination (J2000.0)
23- 28 F6.2 deg GLON Galactic longitude
30- 35 F6.2 deg GLAT Galactic latitude
37- 41 F5.1 d Per Mira period
43- 47 F5.2 mag Jmag J magnitude SAAO system
49- 53 F5.2 mag Hmag H magnitude SAAO system
55- 59 F5.2 mag Kmag K magnitude SAAO system
61- 65 F5.2 mag Lmag L magnitude SAAO system
67- 71 F5.2 mag AV Interstellar extinction in V band
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Acknowledgements:
Robin Catchpole, catchpol(at)ast.cam.ac.uk
(End) R. Catchpole [Inst. of Astronomy, UK], P. Vannier [CDS] 15-Oct-2015