Study of NGC 5128 Globular Clusters Under Multivariate Statistical Paradigm

Chattopadhyay, Asis Kumar; Chattopadhyay, Tanuka; Davoust, E.; Mondal, Saptarshi; Шарина, М. Е.

doi:10.1088/0004-637x/705/2/1533

Cited by 32 publications

(28 citation statements)

References 76 publications

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“…Cen itself may have originated from the nuclear star cluster of an accreted dwarf (Bekki & Freeman 2003). Similar suggestions have been made for a group of clusters in NGC 5128 (Peng et al 2002; Chattopadhyay et al 2009). The recent or ongoing star formation in ESO 243–49 may have been triggered by the passage and tidal disruption of the satellite galaxy, perhaps along the south‐west to north‐east direction, since uvw 2 emission is stronger on that side ().…”

Section: Discussionsupporting

confidence: 81%

Discovery of an optical counterpart to the hyperluminous X-ray source in ESO 243-49

Soria¹,

Hau²,

Graham³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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The existence of black holes of masses – has important implications for the formation and evolution of star clusters and supermassive black holes. One of the strongest candidates to date is the hyperluminous X‐ray source (HLX1), possibly located in the S0–a galaxy ESO 243–49, but the lack of an identifiable optical counterpart had hampered its interpretation. Using the Magellan telescope, we have discovered an unresolved optical source with mag and mag within HLX1’s positional error circle. This implies an average X‐ray/optical flux ratio . Taking the same distance as ESO 243–49, we obtain an intrinsic brightness mag, comparable to that of a massive globular cluster. Alternatively, the optical source is consistent with a main‐sequence M star in the Galactic halo (for example an M4.4 star at kpc). We also examined the properties of ESO 243–49 by combining Swift/Ultraviolet/Optical Telescope (UVOT) observations with stellar population modelling. We found that the overall emission is dominated by a ‐Gyr‐old stellar population, but the UV emission at Å is mostly due to ongoing star formation at a rate of yr−1. The UV emission is more intense (at least a enhancement above the mean) north‐east of the nucleus, in the same quadrant as HLX1. With the combined optical and X‐ray measurements, we put constraints on the nature of HLX1. We rule out a foreground star and a background AGN. Two alternative scenarios are still viable. HLX1 could be an accreting intermediate mass black hole in a star cluster, which may itself be the stripped nucleus of a dwarf galaxy that passed through ESO 243–49, an event which might have caused the current episode of star formation. Or, it could be a neutron star in the Galactic halo, accreting from an M4–M5 donor star.

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Section: Discussionsupporting

confidence: 81%

Discovery of an optical counterpart to the hyperluminous X-ray source in ESO 243-49

Soria¹,

Hau²,

Graham³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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“…EOs were detected in a large number of elliptical galaxies: NGC 5128 (Gomez et al 2006;McLaughlin et al 2008;Chattopadhyay et al 2009;Taylor et al 2010;Mouhcine et al 2010 (Haşegan et al 2005;Evstigneeva et al 2008;Brodie et al 2011;Chies-Santos et al 2011), M 84 (Chies-Santos et al 2011, the central galaxy of the Fornax Cluster NGC 1399 (Richtler et al 2005;Evstigneeva et al 2007;Hilker et al 2007;Evstigneeva et al 2008;Chilingarian et al 2011), NGC 3923 (Norris & Kannappan 2011), NGC 4476 (Haşegan et al 2005), NGC 5846 (Chies-Santos et al 2006), NGC 4696 (Mieske et al 2007), NGC 3311 ), IC 4041, NGC 4889, IC 3998, IC 4030, IC 4041, and NGC 4908 (Chiboucas et al 2011), NGC 4874 (Madrid et al 2010Chiboucas et al 2011), NGC 1132(Madrid 2011), NGC 1275(Penny et al 2012, NGC 4365 (Blom et al 2012), NGC 1316 (Goudfrooij 2012), NGC 1199(Da Rocha et al 2011, and ESO325-G004 (Blakeslee & Barber 2008).…”

Section: Eos In Early-type Galaxiesmentioning

confidence: 99%

A catalog of extended clusters and ultra-compact dwarf galaxies

Kroupa

2012

A&A

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Context. In the past decade, very extended old stellar clusters with masses in the range from a few 10 4 to 10 8 M and effective radii larger than 10 pc have been found in various types of galaxies in different environments. Objects with masses comparable to normal globular clusters (GCs) are called extended clusters (ECs), while objects with masses in the dwarf galaxy regime are called ultra-compact dwarf galaxies (UCDs). Aims. The paper analyses the observational parameters total luminosity, M V , effective radius, r eff , and projected distance to the host galaxy, R proj , of all known ECs and UCDs and the dependence of these parameters on the type and the total luminosity of their host galaxy. Methods. We searched the available literature to compile a catalog of star clusters with effective radii larger than 10 pc. As there is no clear distinction between ECs and UCDs, both types of objects will be called extended stellar objects -abbreviated "EOs" -in this paper.Results. In total, we found 813 EOs of which 171 are associated with late-type galaxies and 642 EOs associated with early-type galaxies. EOs cover a luminosity range from about M V = −4 to −14 mag. However, the vast majority of EOs brighter than M V = −10 mag are associated with giant elliptical galaxies. At each magnitude extended objects are found with effective radii between 10 pc and an upper size limit, which shows a clear trend: the more luminous the object the larger is the upper size limit. For EOs associated with early-and late-type galaxies, the EO luminosity functions peak at −6.40 mag and −6.47 mag, respectively, which is about one magnitude fainter than the peak of the GC luminosity function. EOs and GCs form a coherent structure in the r eff vs. M V parameter space, while there is a clear gap between EOs and early-type dwarf galaxies. However, there is a small potential overlap at the high-mass end, where the most extended EOs are close to the parameters of some compact elliptical galaxies. We compare the EO sample with the numerical models of a previous paper and conclude that the parameters of the EO sample as a whole can be very well explained by a star cluster origin, where EOs are the results of merged star clusters of cluster complexes.

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“…Shopbell, Bland‐Hawthorn & Malin 1993; Ferrarese et al 2007); tip of the red giant branch (RGB; e.g. Soria et al 1996; Rejkuba 2004; Rizzi et al 2007); globular cluster radius (Chattopadhyay et al 2009); globular cluster luminosity function (Harris et al 1984); planetary nebula luminosity function (Hui et al 1993; Ciardullo et al 2002); Mira variables (Rejkuba 2004).…”

Section: Introductionmentioning

confidence: 99%

Triggered star formation in the inner filament of Centaurus A

Crockett

Shabala

Kaviraj

et al. 2012

Monthly Notices of the Royal Astronomical Society

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We present recent Hubble Space Telescope observations of the inner filament of Centaurus A, using the new Wide Field Camera 3 (WFC3) F225W, F657N and F814W filters. We find a young stellar population near the south-west tip of the filament. Combining the WFC3 data set with archival Advanced Camera for Surveys (ACS) F606W observations, we are able to constrain the ages of these stars to ???10Myr, with best-fitting ages of 1-4Myr. No further recent star formation is found along the filament. Based on the location and age of this stellar population, and the fact that there is no radio lobe or jet activity near the star formation, we propose an updated explanation for the origin of the inner filament. Sutherland et al. suggested that radio jet-induced shocks can drive the observed optical line emission. We argue that such shocks can naturally arise due to a weak cocoon-driven bow shock (rather than from the radio jet directly), propagating through the diffuse interstellar medium from a location near the inner northern radio lobe. The shock can overrun a molecular cloud, triggering star formation in the dense molecular cores. Ablation and shock heating of the diffuse gas then give rise to the observed optical line and X-ray emission. Deeper X-ray observations should show more diffuse emission along the filament. ?? 2012 The Authors Monthly Notices of the Royal Astronomical Society ?? 2012 RAS

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Study of NGC 5128 Globular Clusters Under Multivariate Statistical Paradigm

Cited by 32 publications

References 76 publications

Discovery of an optical counterpart to the hyperluminous X-ray source in ESO 243-49

Discovery of an optical counterpart to the hyperluminous X-ray source in ESO 243-49

A catalog of extended clusters and ultra-compact dwarf galaxies

Triggered star formation in the inner filament of Centaurus A

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