Carbon star survey in the Local Group - VIII. Probing the stellar halo of NGC 147

被引:32
作者
Battinelli, P
Demers, S
机构
[1] Osserv Astron Roma, INAF, I-00136 Rome, Italy
[2] Univ Montreal, Dept Phys, Montreal, PQ H3C 3J7, Canada
关键词
galaxies : individual : NGC 147; galaxies : stellar content; galaxies : structure;
D O I
10.1051/0004-6361:20034024
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We have imaged a 42' x 28' field centered on the spheroidal galaxy NGC 147 to Study its AGB Population and determine the main structural properties of this M 3 1 companion. This field was observed through two broadband (R and I) and two narrowband (CN and TiO) filters. following the standard approach of our systematic survey of C stars in nearby galaxies. We identified 288 C stars in NGC 147. The average I-magnitude of Such sample of C stars is <1> = 20.31 with sigma = 0.40. If we adopt a distance modulus mu(0) = 24.39, derived from the luminosity of both the tip of the Led giant branch (TRGB) and the horizontal branch (HB) by Hart et al.. we conclude that the average absolute I-magnitude of C stars is <M-1> = -4.39, thus slightly under luminous with respect to what was found for other galaxies in our survey. From the radial Surface profile we derive a scale length of 4.1 +/- 0.1' and a tidal radius r(1) = 33.9 +/- 2.4', a value quite larger than previous estimates. The C star Population shows a scale length remarkably similar, thus suggesting that intermediate-age stars in NGC 147 are well mixed with the older Population. Finally. the overall C/M ratio is 0.24 +/- 0.02 and its local values increase monotonically from the center LIP to 3.5 scale lengths (beyond which Counts become too low to yield reliable C/M ratios). Such radial behaviour implies a corresponding decrease of about 0.4 dcx in [Fe/H], confirming a well defined metallicity gradient in NGC 147.
引用
收藏
页码:33 / 40
页数:8
相关论文
共 36 条
[1]   A carbon star survey of the local group dwarf galaxies. I. IC 1613 [J].
Albert, L ;
Demers, S ;
Kunkel, WE .
ASTRONOMICAL JOURNAL, 2000, 119 (06) :2780-2788
[2]   DDO 187: Do dwarf galaxies have extended, old halos? [J].
Aparicio, A ;
Tikhonov, N ;
Karachentsev, I .
ASTRONOMICAL JOURNAL, 2000, 119 (01) :177-187
[3]   The spatial and age distribution of stellar populations in DDO 190 [J].
Aparicio, A ;
Tikhonov, N .
ASTRONOMICAL JOURNAL, 2000, 119 (05) :2183-2193
[4]   Carbon star survey in the local group. V. The outer disk of M31 [J].
Battinelli, P ;
Demers, S ;
Letarte, B .
ASTRONOMICAL JOURNAL, 2003, 125 (03) :1298-1308
[5]   LATE-TYPE STARS IN M31 .1. PHOTOMETRIC-STUDY OF AGB STARS AND METALLICITY GRADIENTS [J].
BREWER, JP ;
RICHER, HB ;
CRABTREE, DR .
ASTRONOMICAL JOURNAL, 1995, 109 (06) :2480-2502
[6]   THE DWARF SPHEROIDAL COMPANIONS TO M31 - SURFACE-BRIGHTNESS PROFILES [J].
CALDWELL, N ;
ARMANDROFF, TE ;
SEITZER, P ;
DACOSTA, GS .
ASTRONOMICAL JOURNAL, 1992, 103 (03) :840-&
[7]   AGB stars in the Magellanic Clouds - I. The C/M ratio [J].
Cioni, MRL ;
Habing, HJ .
ASTRONOMY & ASTROPHYSICS, 2003, 402 (01) :133-140
[8]  
COX AN, 2000, ALLENS ASTROPHYSICAL, P392
[9]   Carbon star survey in the Local Group - VII. NGC 3109 a galaxy without a stellar halo [J].
Demers, S ;
Battinelli, P ;
Letarte, B .
ASTRONOMY & ASTROPHYSICS, 2003, 410 (03) :795-801
[10]   C star survey of local group dwarf galaxies. III. The Sagittarius dwarf irregular and the Leo I dwarf spheroidal galaxies [J].
Demers, S ;
Battinelli, P .
ASTRONOMICAL JOURNAL, 2002, 123 (01) :238-243