Centaurus A

Ebneter, K.; Balick, Bruce

doi:10.1086/131239

Cited by 39 publications

(38 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Clearly, the dust lane, gas, and young star formation that are obvious in the inner 5 kpc of the galaxy indicate a relatively recent satellite accretion event (less than 500 Myr ago; see Ebneter & Balick 1983). In addition, the many faint arcs and ripples superposed on the smooth halo light extending out 15 kpc or more (see Peng et al 2002) are strongly suggestive of mergers from much longer ago.…”

Section: Comments and Discussionmentioning

confidence: 95%

Wide-Field Washington Photometry of the NGC 5128 Globular Cluster System. II. Large-Scale Properties of the System

Harris

Geisler

2004

Astron J

View full text Add to dashboard Cite

Building on the CMT 1 photometric database presented in Paper I, in this paper we derive the large-scale properties of the globular cluster system (GCS) in NGC 5128, the nearest giant elliptical and the dominant galaxy in the Centaurus group. In global terms, it has a smaller total population than previously thought: we estimate 980 AE 120 clusters over all magnitudes, yielding a specific frequency S N ¼ 1:4 AE 0:2, with a steep projected radial distribution $ r À2 . The luminosity distribution of the clusters resembles that of an old, normal GC luminosity function (Gaussian-like with peak at M V ' À7:4 and dispersion of '1.3 mag), but these parameters are unfortunately quite uncertain because of the system's low population and the heavy field contamination. Using the metallicity-sensitive C À T 1 color index, we discuss the metallicity distribution function (MDF) for a subsample of 211 previously identified clusters, all on a homogeneous photometric system. We find the MDF to be strongly bimodal, with metallicity peaks at ½Fe=H ¼ À1:55 and À0.55 and with nearly equal numbers of clusters in each of the metal-poor and metal-rich modes. The combined evidence from the system's low specific frequency, the MDF, and the isophotal shell features in the halo light make a ''major merger'' a plausible model for the formation history of this giant E galaxy. However, the progenitor galaxies must have been more gas-rich than in any present-day mergers or starbursts. Finally, we present a list of 327 new cluster candidates not identified in any previous surveys; most of these are in the less well studied bulge region of the galaxy and along the minor axis.

show abstract

Section: Comments and Discussionmentioning

confidence: 95%

Wide-Field Washington Photometry of the NGC 5128 Globular Cluster System. II. Large-Scale Properties of the System

Harris

Geisler

2004

Astron J

View full text Add to dashboard Cite

show abstract

“…MRC B1322À427: The well-studied low-luminosity radio galaxy Centaurus A (see review by Ebneter & Balick 1983). The flux density at 843 MHz was determined from the radio spectrum.…”

Section: Comments On Individual Sourcesmentioning

confidence: 99%

The Molonglo Southern 4 Jy Sample (MS4). I. Definition

Burgess

Hunstead

2006

Astron J

View full text Add to dashboard Cite

We have defined a complete sample of 228 southern radio sources at 408 MHz with integrated flux densities S 408 > 4:0 Jy, Galactic latitude jbj > 10 , and declination À85 < < À30 . The main finding survey used was the Molonglo Reference Catalogue. We describe in detail how the Molonglo Southern 4 Jy sample (MS4) was assembled and its completeness assessed. Sources in the sample were imaged at 843 MHz with the Molonglo Observatory Synthesis Telescope to obtain positions accurate to about 1 00 , as well as flux densities and angular sizes; follow-up radio and optical observations are presented in Paper II. Radio spectra for the MS4 have been compiled from the literature and used to estimate flux densities at 178 MHz. The strong-source subset of MS4, with S 178 > 10:9 Jy (SMS4), provides a southern sample closely equivalent to the well-studied northern 3CRR sample. Comparison of SMS4 with 3CRR shows a reassuring similarity in source density and median flux density between the two samples.

show abstract

“…Further out, faint shells can be seen that are presumably the remnants of a long-ago satellite accretion (Malin et al 1983), as well as faint filaments of ionized gas and young stars along the northern radio and X-ray jet (Graham 1998;Mould et al 2000;Rejkuba et al 2001;Rejkuba et al 2002), a young blue arc of star formation (Peng et al 2002), and diffuse radio lobes that extend out hundreds of kiloparsecs (Morganti et al 1999;Feain et al 2009). For extensive reviews we refer to Ebneter & Balick (1983) and Israel (1998). This range of properties often prompts the response that anything learned about the old stellar population of NGC 5128 will be "anomalous" and thus not applicable to other giant ellipticals.…”

Section: Introductionmentioning

confidence: 99%

How old are the stars in the halo of NGC 5128 (Centaurus A)?

Rejkuba¹,

Harris

Greggio

et al. 2011

A&A

View full text Add to dashboard Cite

Context. NGC 5128 (Centaurus A) is, at the distance of just 3.8 Mpc, the nearest easily observable giant elliptical galaxy. Therefore it is the best target to investigate the early star formation history of an elliptical galaxy. Aims. Our aims are to establish when the oldest stars formed in NGC 5128, and whether this galaxy formed stars over a long period. Methods. We compare simulated colour−magnitude diagrams with the deep ACS/HST photometry. The simulations assume in input either the observed metallicity distribution function, based on the colour distribution of the upper red giant branch stars, or the closed box chemical enrichment. Simulations are constructed for single age bursts using BASTI evolutionary isochrones; more complex star formation histories are constructed as well by combining several individual simulations. Comparisons with data are made by fitting the whole colour−magnitude diagram as well as the the luminosity functions in V and I band. In addition we inspect carefully the red clump and asymptotic giant branch bump luminosities and number counts, since these features are the primary constraints on the ages of the observed stars. Results. We find that that the observed colour−magnitude diagram can be reproduced satisfactorily only by simulations that have the bulk of the stars with ages in excess of ∼10 Gyr, and that the alpha-enhanced models fit the data much better than the solar scaled ones. Data are not consistent with extended star formation over more than 3−4 Gyr. Two burst models, with 70−80% of the stars formed 12 ± 1 Gyr ago and with 20−30% younger contribution with 2−4 Gyr old stars provide the best agreement with the data. The old component spans the whole metallicity range of the models (Z = 0.0001−0.04), while for the young component the best fitting models indicate higher minimum metallicity (∼1/10−1/4 Z ). Conclusions. The bulk of the halo stars in NGC 5128 must have formed at redshift z > ∼ 2 and the chemical enrichment was very fast, reaching solar or even twice-solar metallicity already for the ∼11−12 Gyr old population. The minor young component, adding ∼20−30% of the stars to the halo, and contributing less than 10% of the mass, may have resulted from a later star formation event ∼2−4 Gyr ago.

show abstract

Centaurus A

Cited by 39 publications

References 43 publications

Wide-Field Washington Photometry of the NGC 5128 Globular Cluster System. II. Large-Scale Properties of the System

Wide-Field Washington Photometry of the NGC 5128 Globular Cluster System. II. Large-Scale Properties of the System

The Molonglo Southern 4 Jy Sample (MS4). I. Definition

How old are the stars in the halo of NGC 5128 (Centaurus A)?

Contact Info

Product

Resources

About