J/A+A/442/165 IJKs photometry of late-type stars in Draco dSph (Cioni+, 2005)
The Draco dwarf galaxy in the near-infrared.
Cioni M.-R.L., Habing H.J.
<Astron. Astrophys. 442, 165 (2005)>
=2005A&A...442..165C 2005A&A...442..165C
ADC_Keywords: Galaxies, photometry ; Photometry, infrared ; Stars, late-type
Keywords: stars: late-type - stars: distances - galaxies: Local Group -
galaxies: photometry - infrared stars - stars: carbon
Abstract:
With the William Herschel Telescope in La Palma we made IJKs
observations of an area of about 40'x30' of the Local Group galaxy
Draco. This allows us to describe Draco's late-type stellar population
across the whole galaxy at a photometric level 2mag deeper than the
2MASS survey. We detected the red giant branch (RGB) and measured the
magnitude of the tip of the RGB in the three bands. From that in the
I band we obtain a distance modulus of
(m-M)_0=19.49±0.06(stat)±0.15(sys), in excellent agreement with a
measurement from RR Lyrae stars. The peak of the (J-Ks)0 histogram
at different MKs suggests that Draco has a mean [Fe/H]=-1.95±1.26
while fiducial RGB tracks of Galactic globular clusters indicate a
mean [Fe/H]=-1.33±0.72 where the error corresponds to the spread
around the mean value. There are significant differences between the
colour-magnitude diagrams of stars in the inner, medium and outer
areas of the galaxy. A metal poor (Z=0.0004) intermediate-age
population (about 1.6Gyr old) is clearly present and emerges in
particular between 6' and 12' from the centre of the galaxy. A few
additional carbon star candidates have been identified from both their
location in the colour-magnitude diagram and from an indication of
variability. The large scale distribution of late-type stars is smooth
but irregular in shape; this points at a variation of inclination with
radius.
Description:
Photometry of 2570 stars detected in IJKs covering the Draco dwarf
Local Group galaxy is presented. For each stars equatorial
coordinates, magnitudes and errors are given as well as source
extraction flags.
Objects:
-------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------
17 20 12.4 +57 54 55 Draco = UGC 10822
-------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 64 2570 IJKs photometry of 2570 stars in Draco
--------------------------------------------------------------------------------
See also:
J/A+A/429/837 : IJKs photometry of late-type stars in NGC 6822 (Cioni+, 2005)
J/AJ/121/841 : RV photometry of Draco dwarf spheroidal galaxy (Piatek+, 2001)
J/AJ/123/2511 : RV photometry of Draco dwarf spheroidal galaxy (Piatek+, 2002)
J/ApJS/145/245 : SDSS stars in Draco dwarf spheroidal galaxy (Rave+, 2003)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.6 deg RAdeg Right ascension J2000 (degrees)
13- 21 F9.6 deg DEdeg Declination J2000 (degrees)
23- 27 F5.2 mag Imag I magnitude
30- 33 F4.2 mag e_Imag Error in I magnitude
35 I1 --- f_Imag [0/2] SExtractor flag in I magnitude (1)
37- 41 F5.2 mag Jmag J magnitude
44- 47 F4.2 mag e_Jmag Error in J magnitude
49 I1 --- f_Jmag [0/2] SExtractor flag in J magnitude (1)
51- 55 F5.2 mag Ksmag Ks magnitude
58- 61 F4.2 mag e_Ksmag Error in Ks magnitude
63 I1 --- f_Ksmag [0/2] SExtractor flag in Ks magnitude (1)
--------------------------------------------------------------------------------
Note (1): SExtractor flag is as follows:
1 = object that has bright neighbours or bad pixels affecting
more than 10% of the integrated area
2 = object that was originally blended with another
--------------------------------------------------------------------------------
Acknowledgements: Maria-Rosa Cioni, mrc(at)roe.ac.uk
(End) Maria-Rosa Cioni [IfA, Edinburgh], Patricia Vannier [CDS] 05-Sep-2005