J/AJ/114/1488 Globulars in M31 (Holland+ 1997)
Deep HST V- and I-band observations of two globular clusters in the halo of M31
Holland S., Fahlman G.G., Richer H.B.
<Astron. J. 114, 1488 (1997)>
=1997AJ....114.1488H 1997AJ....114.1488H
ADC_Keywords: Clusters, globular ; Photometry
Mission_Name: HST
Abstract:
We present deep (V≃27) V- and I-band stellar photometry of G302 and
G312, two globular star clusters in the halo of M31. These data were
obtained using the Hubble Space Telescope's Wide Field/Planetary
Camera 2. We find iron abundances of [Fe/H]=-1.85±0.12 for G302
and [Fe/H]=-0.56±0.03 for G312, consistent with spectroscopic
measurements. The color-magnitude diagrams for each cluster show no
evidence for an intermediate-aged population of stars, or a second
parameter effect in the morphology of the horizontal branch. G302
shows no evidence for a color gradient but the inner regions of G312
are bluer than the outer regions. G312 shows no evidence of
ellipticity or an extended halo of stars. G302 has a projected
ellipticity of ε=0.195±0.012 with the projected major axis
oriented towards the center of M31. G302 also shows evidence of an
extended asymmetric stellar halo extending to at least twice the
fitted Michie-King tidal radius. The amount of mass beyond the tidal
radius of G302 is consistent with the stellar escape rates which have
been predicted by N-body simulations of globular clusters in the
Galactic tidal field.
(c) 1997 American Astronomical Society.
Objects:
----------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------
00 45 25.2 +41 05 30 G302 = SKHB 302 = Bol 240
00 45 58.8 +40 42 32 G312 = SKHB 312 = Bol 379
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 64 13321 Stellar photometry for G302 and the surrounding fields
table4.dat 64 3349 Stellar photometry for G312 and the surrounding fields
table5.dat 70 626 Stellar photometry for G302
table6.dat 70 325 Stellar Photometry for G312
tables.tex 101 17741 AASTeX version of the tables
tables.ps 72 29775 PostScript version of the tables
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- CCD CCD the star was observed on
7- 10 I4 --- ID Identification number (1)
12- 18 F7.3 pix Xpos X pixel coordinate (2)
20- 26 F7.3 pix Ypos Y pixel coordinate (2)
28- 33 F6.3 mag Vmag V-band magnitude
35- 39 F5.3 mag e_Vmag 1-sigma uncertainty in Vmag
41- 45 F5.3 --- 2_Vmag Value of the DAOPHOT Chi statistics for Vmag
47- 52 F6.3 mag Imag I-band magnitude
54- 58 F5.3 mag e_Imag 1-sigma uncertainty in Imag
60- 64 F5.3 --- 2_Imag Value of the DAOPHOT Chi statistics for Imag
--------------------------------------------------------------------------------
Note (1): Identification numbers are only unique for stars on a given CCD.
Note (2): 1 pix = 0.1".
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- CCD CCD the star was observed on
7- 10 I4 --- ID Identification number
12- 18 F7.3 pix Xpos X pixel coordinate (1)
20- 26 F7.3 pix Ypos Y pixel coordinate (1)
28- 32 F5.3 arcsec Dist Distance of star from cluster center
34- 39 F6.3 mag Vmag V-band magnitude
41- 45 F5.3 mag e_Vmag 1-sigma uncertainty in Vmag
47- 51 F5.3 --- 2_Vmag Value of the DAOPHOT Chi statistics for Vmag
53- 58 F6.3 mag Imag I-band magnitude
60- 64 F5.3 mag e_Imag 1-sigma uncertainty in Imag
66- 70 F5.3 --- 2_Imag Value of the DAOPHOT Chi statistics for Imag
--------------------------------------------------------------------------------
Note (1): 1 pix = 0.1".
--------------------------------------------------------------------------------
Origin: AAS CD-ROM series, Volume 9, 1997 Lee Brotzman [ADS] 04-Nov-1997
(End) [CDS] 05-Feb-1998