SIMBAD references

1999MNRAS.306..857C - Mon. Not. R. Astron. Soc., 306, 857-896 (1999/July-2)

The ROSAT Brightest Cluster Sample - III. Optical spectra of the central cluster galaxies.


Abstract (from CDS):

We present new spectra of dominant galaxies in X-ray-selected clusters of galaxies, which combine with our previously published spectra to form a sample of 256 dominant galaxies in 215 clusters. 177 of the clusters are members of the ROSAT Brightest Cluster Sample (BCS; Ebeling et al.), and 17 have no previous measured redshift. This is the first paper in a series correlating the properties of brightest cluster galaxies and their host clusters in the radio, optical and X-ray wavebands.

27 per cent of the central dominant galaxies have emission-line spectra, all but five with line intensity ratios typical of cooling flow nebulae. A further 6 per cent show only [N ii]λλ6548,6584 with Hα in absorption. We find no evidence for an increase in the frequency of line emission with X-ray luminosity. Purely X-ray-selected clusters at low redshift have a higher probability of containing line emission. The projected separation between the optical position of the dominant galaxy and its host cluster X-ray centroid is less for the line-emitting galaxies than for those without line emission, consistent with a closer association of the central galaxy and the gravitational centre in cooling flow clusters.

The more Hα-luminous galaxies have larger emission-line regions and show a higher ratio of Balmer to forbidden line emission, although there is a continuous trend of ionization behaviour across four decades in Hα luminosity. Galaxies with the more luminous line emission [L(Hα)> 1041erg.s–1] show a significantly bluer continuum, whereas lower luminosity and [N ii]-only line emitters have continua that differ little from those of non-line-emitting dominant galaxies. Values of the Balmer decrement in the more luminous systems commonly imply intrinsic reddening of E(B-V)∼0.3 and, when this is corrected for, the excess blue light can be characterized by a population of massive young stars. Several of the galaxies require a large population of O stars, which also provide sufficient photoionization to produce the observed Hα luminosity. The large number of lower mass stars relative to the O-star population suggests that this anomalous population is caused by a series of starbursts in the central galaxy.

The lower Hα-luminosity systems show a higher ionization state and few massive stars, requiring instead the introduction of a harder source of photoionization, such as turbulent mixing layers, or low-level nuclear activity. The line emission from the systems showing only [N ii] is very similar to low-level LINER activity commonly found in many normal elliptical galaxies.

Abstract Copyright: 1999 RAS

Journal keyword(s): surveys - galaxies: clusters: general - cooling flows - galaxies: elliptical and lenticular, cD - galaxies: stellar content - X-rays: galaxies

VizieR on-line data: <Available at CDS (J/MNRAS/306/857): table1.dat table2.dat table3.dat notes.dat>

Nomenclature: Tables 1, 2, 3: [CAE99] ACO NNNN, [CAE99] ACO NNNN a, [CAE99] ACO NNNNa, [CAE99] ACO NNNNa a, [CAE99] Z NNNN, [CAE99] Z NNNN a, [CAE99] RX JHHMM.m+DDMM, [CAE99] RX JHHMM.m+DDMM a, [CAE99] RX JHHMM.m+DDMM W, N=213+41+38.

Simbad objects: 329

goto Full paper

goto View the references in ADS

To bookmark this query, right click on this link: simbad:1999MNRAS.306..857C and select 'bookmark this link' or equivalent in the popup menu