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Post Info TOPIC: Messier 49


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Posts: 131433
Date:
Arp 134
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Title: A deeper look at the X-ray point source population of NGC 4472
Author: T. D. Joseph, T. J. Maccarone, R. P. Kraft, G. R. Sivakoff

In this paper we discuss the X-ray point source population of NGC 4472, an elliptical galaxy in the Virgo cluster. We used recent deep Chandra data combined with archival Chandra data to obtain a 380 ks exposure time. We find 238 X-ray point sources within 3.7' of the galaxy centre, with a completeness flux, F(X,0.5-2 keV)= 6.3 x 10^-16 ergs^-1 cm^-2. Most of these sources are expected to be low mass X-ray binaries. We finding that, using data from a single galaxy which is both complete and has a large number of objects (~ 100) below 10^38 ergs^-1, the X-ray luminosity function is well fit with a single power law model. By cross matching our X-ray data with both space based and ground based optical data for NGC 4472, we find that 80 of the 238 sources are in globular clusters. We compare the red and blue globular cluster subpopulations and find red clusters are nearly six times more likely to host an X-ray source than blue clusters. We show that there is evidence that these two subpopulations have significantly different X-ray luminosity distributions. Source catalogues for all X-ray point sources, as well as any corresponding optical data for globular cluster sources, are also presented here.

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Posts: 131433
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RE: Messier 49
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Title: The halo of M49 and its environment as traced by planetary nebulae
Author: J. Hartke, M. Arnaboldi, A. Longobardi, O. Gerhard, K. C. Freeman, S. Okamura, F. Nakata

The galaxy M49 (NGC 4472) is the brightest early-type galaxy in the Virgo Cluster. It is located in Subcluster B and has an unusually blue, metal-poor outer halo. Planetary nebulae (PNe) are excellent tracers of diffuse galaxy and intragroup light. We present a photometric survey of PNe in the galaxy's extended halo to characterise its PN population, as well as the surrounding intragroup light (IGL) of the Subcluster B. PNe were identified based on their bright [OIII]5007 \AA\ emission and absence of a broad-band continuum. We identify 738 PNe out to a radius of 155 kpc from M49's centre from which we define a complete sample of 624 PNe within a limiting magnitude of m_5007=28.8. Comparing the PN number density to the broad-band stellar surface brightness profile, we find a variation of the PN-specific frequency (alpha-parameter) with radius. The outer halo beyond 60 kpc has a 3.2 times higher alpha-parameter compared to the main galaxy halo, which is likely due to contribution from the surrounding blue IGL. We use the Planetary Nebulae Luminosity Function (PNLF) as an indicator of distance and stellar population. Its slope, which correlates empirically with galaxy type, varies within the inner halo. In the eastern quadrant of M49, the PNLF slope is shallower, indicating an additional localised, bright PN population following an accretion event, likely that of the dwarf irregular galaxy VCC1249. We also determined a distance modulus of mu = 31.290.08 for M49, corresponding to a physical distance of 18.10.6 Mpc, which agrees with a recent surface-brightness fluctuations distance. The PN populations in the outer halo of M49 are consistent with the presence of a main Sersic galaxy halo with a slight (B-V) colour gradient of 10^-4 mag/arcsec surrounded by intragroup light with a very blue colour of (B-V)=0.25 and a constant surface brightness mu_V=28.0 mag/arcsec2.

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Posts: 131433
Date:
NGC 4472
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Messier 49 (also known as M 49 or NGC 4472) is an elliptical galaxy located about 49 million light-years away in the equatorial constellation of Virgo. This galaxy was discovered by French astronomer Charles Messier on February 19, 1771. Messier 49 is positioned 4.1 west-southwest of the star Epsilon Virginis
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Posts: 131433
Date:
Messier 49
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Title: Stellar Populations in the Outer Halo of the Massive Elliptical M49
Authors: Chris Mihos, Paul Harding, Craig Rudick, John Feldmeier

We use deep surface photometry of the giant elliptical M49 (NGC 4472), obtained as part of our survey for diffuse light in the Virgo Cluster, to study the stellar populations in its outer halo. Our data trace M49's stellar halo out to ~ 100 kpc (7 Re), where we find that the shallow colour gradient seen in the inner regions becomes dramatically steeper. The outer regions of the galaxy are quite blue (B-V ~ 0.7); if this is purely a metallicity effect, it argues for extremely metal poor stellar populations with [Fe/H] < -1. We also find that the extended accretion shells around M49 are distinctly redder than the galaxy's surrounding halo, suggesting that we are likely witnessing the buildup of both the stellar mass and metallicity in M49's outer halo due to late time accretion. While such growth of galaxy halos is predicted by models of hierarchical accretion, this growth is thought to be driven by more massive accretion events which have correspondingly higher mean metallicity than inferred for M49's halo. Thus the extremely metal-poor nature of M49's extended halo provides some tension against current models for elliptical galaxy formation.

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