J/A+A/483/769 HST VI photometry of 3 globulars in M31 (Fuentes-Carrera+, 2008)
Evidence for metallicity spreads in three massive M31 globular clusters.
Fuentes-Carrera I., Jablonka P., Sarajedini A., Bridges T., Djorgovski G.,
Meylan G.
<Astron. Astrophys. 483, 769 (2008)>
=2008A&A...483..769F 2008A&A...483..769F
ADC_Keywords: Galaxies, nearby ; Clusters, globular ; Photometry, HST
Keywords: galaxies: evolution - galaxies: Local Group -
galaxies: star clusters - Galaxy: globular clusters: general
Abstract:
We quantify the intrinsic width of the red giant branches of three
massive globular clusters in M 31 in a search for metallicity spreads
within these objects.
We present HST/ACS observations of three massive clusters in M 31,
G78, G213, and G280. A thorough description of the photometry
extraction and calibration is presented. After derivation of the
color-magnitude diagrams, we quantify the intrinsic width of the red
giant branch of each cluster.
Description:
The Tables present the individual photometric measurements of stars in
the field of view of the globular clusters G78 (table2a.dat), G213
(table2b.dat) and G280 (table2c.dat) in M31. Observations of the three
clusters and their surrounding fields were done with the High
Resolution Channel (HRC) of the Advanced Camera for Surveys (ACS)
aboard HST. Four images of each globular cluster were taken using the
F606W (close to V) and F814W (close to I) filters with total
integration time of 505x4=2020s and 715x4=2860s, respectively. Images
were dithered following the four-point dither pattern known as
ACS-HRC-DITHER-BOX. The instrumental signature was removed from these
images (bias, dark and flat-field correction) by the
on-the-fly-reprocessing (OTFR) performed by CALACS. Images were
corrected for geometric distortion and combined using the MultiDrizzle
task of the STSci pipeline incorporated in PyRAF (Koekemoer et
al., 2002, The 2002 HST Calibration Workshop, p.337
(2002hstc.conf..337K)).
Photometry was extracted using the DAOPHOT/ALLSTAR routines (Stetson
1994PASP..106..250S 1994PASP..106..250S). Point-spread functions (PSFs) were constructed
with DAOPHOT and stars were measured using the ALLSTAR routine. A
detailed description of the procedure is presented in the paper.
In order to derive the color-magnitude diagrams (CMD) of each cluster,
stars were statistically selected according to their photometric
error, chi-square and sharpness values in order to get rid of spurious
photometric detections that might contaminate the results. Remaining
stars are indicated in the Tables with a "selection FLAG' value equal
to 1. All values are in instrumental magnitudes.
Objects:
------------------------------------------------------------------
RA (2000) DE Designation(s) (Table)
------------------------------------------------------------------
00 41 01.3 +41 13 45 G78 = SKHB 78 = Bol 23 (table2a)
00 43 14.4 +41 07 21 G213 = SKHB 213 = Bol 158 (table2b)
00 44 29.6 +41 21 35 G280 = SKHB 280 = Bol 225 (table2c)
-----------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2a.dat 91 8805 Individual photometric measurements for stars in
the field-of-view of globular cluster G78 in M31
table2b.dat 91 15233 Individual photometric measurements for stars in
the field-of-view of globular cluster G213 in M31
table2c.dat 91 12982 Individual photometric measurements for stars in
the field-of-view of globular cluster G280 in M31
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2?.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- Seq Identification number (1)
7- 13 F7.2 pix Xpos Abscissa of star in the MultiDrizzled image (2)
15- 21 F7.2 pix Ypos Ordinate of star in the MultiDrizzled image (2)
23- 29 F7.4 mag F606 Instrumental magnitude in the F606W filter
31- 37 F7.5 mag e_F606 Photometric error in the F606W filter (3)
39- 46 F8.5 --- chi-F606 Chi-square value in the F606W filter (3)
48- 55 F8.5 --- sh-F606 Sharpness value in the F606W filter (3)
57- 63 F7.4 mag F814 Instrumental magnitude in the F814W filter
65- 71 F7.5 mag e_F814 Photometric error in the F814W filter (3)
73- 80 F8.5 --- chi-F814 Chi-square value in the F814W filter (3)
82- 89 F8.5 --- sh-F814 Sharpness value in the F814W filter (3)
91 I1 --- Flag [0/1] Selection flag (4)
--------------------------------------------------------------------------------
Note (1): Identification number given by DAOPHOT for star identification
Note (2): 1pix=0.027".
Note (3): Values given by ALLSTAR (Stetson, 1994PASP..106..250S 1994PASP..106..250S)
Note (4): 1 indicates that the star survived the statistical selection
discussed in the paper, and 0 that the star was rejected for the
analysis of the CMD.
--------------------------------------------------------------------------------
Acknowledgements:
Isaura Fuentes-Carrera, isaura.fuentes(at)obspm.fr
(End) Patricia Vannier [CDS] 27-Mar-2008