A ROSAT DEEP SURVEY .6. ACTIVE AND PASSIVE X-RAY GALAXIES

被引:45
作者
GRIFFITHS, RE
GEORGANTOPOULOS, I
BOYLE, BJ
STEWART, GC
SHANKS, T
DELLACECA, R
机构
[1] UNIV LEICESTER,DEPT PHYS & ASTRON,LEICESTER LE1 7RH,LEICS,ENGLAND
[2] UNIV CAMBRIDGE,INST ASTRON,CAMBRIDGE CB3 0HA,ENGLAND
[3] UNIV DURHAM,DEPT PHYS,DURHAM DH1 3LE,ENGLAND
关键词
GALAXIES; ELLIPTIC AND LENTICULAR; CD; X-RAYS; GENERAL;
D O I
10.1093/mnras/275.1.77
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We have shown previously that ROSAT deep-survey X-ray sources (to limiting fluxes of similar to 10(-14) erg cm(-2) s(-1), 0.5-2 keV) are predominantly identified with active galactic nuclei, but this paper focuses on the smaller fraction of objects identified with emission-line galaxies and late-type 'passive' galaxies. The nature of the discrete X-ray sources has been directly investigated by means of multi-object spectroscopy of candidate optical counterparts based on positional coincidence to within similar to 15 arcsec. A small number of early-type or 'passive' galaxies are detected within 300 km s(-1) of a common redshift of 0.312, and may be members of a large (14 Mpc) structure. There is no clear evidence for extended intracluster gas, however, and there is no X-ray or optical evidence for a rich cluster. Several possibilities as to the origin of the X-ray emission from these passive galaxies are discussed: (i) active galactic nuclei within otherwise passive galaxies (although no emission lines have been observed); (ii) hot coronae of elliptical galaxies, possibly in the early stages of cooling flows; and (iii) small groups of galaxies, or 'fossil' group emission, centred on the elliptical. Other discrete source detections have included the first examples of starburst and star-forming (narrow emission-line) galaxies in ROSAT deep surveys, of the kind which may also contribute to the XRB in the ROSAT energy range.
引用
收藏
页码:77 / 88
页数:12
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