J/A+A/487/131 JHKs photometry of LPVs in M33 (Cioni+, 2008)
AGB stars as tracers of metallicity and mean age across M33.
Cioni M.-R.L., Irwin M., Ferguson A.M.N., McConnachie A., Conn B.C.,
Huxor A., Ibata R., Lewis G., Tanvir N.
<Astron. Astrophys. 487, 131 (2008)>
=2008A&A...487..131C 2008A&A...487..131C
ADC_Keywords: Galaxies, nearby ; Stars, variable ; Photometry, infrared
Keywords: galaxies: individual: M 33 - stars: late-type -
galaxies: stellar content - Galaxy: abundances - galaxies: structure
Abstract:
Wide-field JHKs near-infrared observations covering an area of
1.8x1.8deg2 centred on M33 were obtained using WFCAM at UKIRT.
These data show a large population of intermediate-age asymptotic
giant branch stars (AGB). We have used both C-type and M-type AGB
stars to determine spatial variations in metallicity and mean age
across the galaxy. We distinguished between C-type and M-type AGB
stars from their location in the colour-magnitude diagram (J-Ks, Ks).
The distribution of these stars is supported by a cross-identification
between our sample and a catalogue of optically confirmed, long-period
variable stars, as well as with the list of sources detected by
Spitzer in the mid-infrared. We calculated the C/M ratio and the
orientation of the galaxy in the sky, and compared the Ks magnitude
distribution with theoretical distributions spanning a range of
metallicities and star formation rates (SFRs). The C/M ratio surface
map confirms a metallicity gradient in the galaxy corresponding to a
spread in [Fe/H]=0.6dex with substructures in the inner and outer
galaxy. Magnitude and colour variations suggest orientation and
extinction effects on the galaxy disc. Maps showing the distribution
of mean age and metallicity obtained from the Ks method suggest that:
the outer galaxy disc/halo is metal poorer than the nuclear region and
metal-rich clumps in the inner galaxy change location with time. The
average outer ring and nuclear stellar population is ∼6Gyr old while
central regions are a few Gyr younger.
Description:
Near-infrared magnitudes for 7650 candidate long-period variables and
847 stars observed by Spitzer across M33 are presented. For each long
period variable equatorial coordinates and near-infrared JHKs
magnitudes are given from UKIRT observations as well as optical r'i'
magnitudes from Hartman et al. (2006, Cat. J/MNRAS/371/1405). The
Spizer ID (McQuinn et al., 2007, Cat. J/ApJ/664/850) identifies
those stars for which we present equatorial coordinates and JHKs
magnitudes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 51 7650 Near-IR magnitudes for Long-Period Variables (LPVs)
table2.dat 59 847 Near-IR magnitudes for stars observed by Spitzer
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See also:
J/AJ/121/870 : BVI photometry of variables in M33 (Macri+, 2001)
J/AJ/132/1361 : RR Lyrae variables in M33 (Sarajedini+, 2006)
J/MNRAS/371/1405 : Variables in M33 (Hartman+, 2006)
J/ApJ/664/850 : Spitzer M33 variables (McQuinn+, 2007)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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2- 10 F9.6 deg RAdeg Right ascension in decimal degrees (J2000.0)
13- 21 F9.6 deg DEdeg Declination in decimal degrees (J2000.0)
23- 27 F5.2 mag i'mag SDSS i' magnitude
29- 33 F5.2 mag r'-i' SDSS r'-i' colour index
35- 39 F5.2 mag Jmag Dereddened Johnson J magnitude (G1)
41- 45 F5.2 mag Hmag Dereddened Johnson H magnitude (G1)
47- 51 F5.2 mag Ksmag Dereddened Johnson Ks magnitude (G1)
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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- 19 A19 --- SSTM3307 Spitzer-ID (JHHMMSS.SS+DDMMSS.s)
22- 30 F9.6 deg RAdeg Right ascension in decimal degrees (J2000.0)
33- 41 F9.6 deg DEdeg Declination (J2000.0)
43- 47 F5.2 mag Jmag Dereddened Johnson J magnitude (G1)
49- 53 F5.2 mag Hmag Dereddened Johnson H magnitude (G1)
55- 59 F5.2 mag Ksmag Dereddened Johnson Ks magnitude (G1)
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Note (G1): Magnitudes are dereddened for galactic foreground extinction
assuming E(B-V)=0.07 and absorptions of: J=0.06, H=0.04 and Ks=0.02mag.
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Acknowledgements:
Maria-Rosa L. Cioni, M.Cioni(at)herts.ac.uk
(End) M.-R.L. Cioni [Univ. of Hertfordshire, UK], P. Vannier [CDS] 06-Jun-2008