The Distribution of Dark Matter in the Halo of the Early-Type Galaxy NGC 4636

Chakrabarty, Dalia; Raychaudhury, Somak

doi:10.1088/0004-6256/135/6/2350

Cited by 19 publications

(21 citation statements)

References 43 publications

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“…Following Chakrabarty & Raychaudhury (2008; hereafter referred to as CR08), we assume a distance of 16 Mpc for NGC 4636 throughout. The location, scale, and basic properties of NGC 4636 are shown in Table 1.…”

Section: Ngc 4636mentioning

confidence: 99%

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Comparing X-Ray and Dynamical Mass Profiles in the Early-Type Galaxy NGC 4636

Johnson¹,

Chakrabarty²,

O’Sullivan³

et al. 2009

ApJ

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We present the results of an X-ray mass analysis of the early-type galaxy NGC 4636, using Chandra data. We have compared the X-ray mass density profile with that derived from a dynamical analysis of the system's globular clusters (GCs). Given the observed interaction between the central active galactic nucleus and the X-ray emitting gas in NGC 4636, we would expect to see a discrepancy in the masses recovered by the two methods. Such a discrepancy exists within the central ∼10 kpc, which we interpret as the result of non-thermal pressure support or a local inflow. However, over the radial range ∼10-30 kpc, the mass profiles agree within the 1σ errors, indicating that even in this highly disturbed system, agreement can be sought at an acceptable level of significance over intermediate radii, with both methods also indicating the need for a dark matter halo. However, at radii larger than 30 kpc, the X-ray mass exceeds the dynamical mass, by a factor of 4-5 at the largest disagreement. A Fully Bayesian Significance Test finds no statistical reason to reject our assumption of velocity isotropy, and an analysis of X-ray mass profiles in different directions from the galaxy center suggests that local disturbances at large radius are not the cause of the discrepancy. We instead attribute the discrepancy to the paucity of GC kinematics at large radius, coupled with not knowing the overall state of the gas at the radius where we are reaching the group regime (>30 kpc), or a combination of the two.

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Section: Ngc 4636mentioning

confidence: 99%

“…Section 2 describes the basic properties of NGC 4636; and Section 3 describes our method for extracting high-resolution mass profiles from Chandra X-ray data. In Section 4, we present our results and comparison to the GC analysis of Chakrabarty & Raychaudhury (2008); and in Section 5, we discuss the implications of our results.…”

Section: Introductionmentioning

confidence: 99%

Comparing X-Ray and Dynamical Mass Profiles in the Early-Type Galaxy NGC 4636

Johnson¹,

Chakrabarty²,

O’Sullivan³

et al. 2009

ApJ

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“…The galaxy NGC4636, has boxy isophotes (Rembold et al 2002) and does not show rotation both along major and minor axes (Davies et al 1993;Bender et al 1994;Rampazzo et al 2005). Indeed, NGC4636 is one of the best targets for studying kinematics of globular clusters since it has an anomalously large number of GCs (Dirsch et al 2005;Chakrabarty & Raychaudhury 2008;Park et al 2010;Lee et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Stellar kinematics and populations out to 1.5 effective radii in the elliptical galaxy NGC 4636

Han

2011

Res. Astron. Astrophys.

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We present high quality long slit spectra along the major and minor axes out to 1.5 effective radius (R e ) of the massive galaxy NGC4636 taken by Hobby-Eberly Telescope (HET). Using Fourier Correlation Quotient (FCQ) method, we measured the stellar line-of-sight velocity distribution along the axes. Furthermore, six Lick/IDS indices (Hβ, Mgb, Fe 5015 , Fe 5270 , Fe 5335 , Fe 5406 ) are derived from the clean spectrum. By comparing the measured absorption line strengths with the predictions of Simple Stellar Populations (SSP) models, we derived ages, total metallicity and α abundance profiles of the galaxy. This galaxy presents old and [α/Fe] over abundant stellar populations. Indeed, using the SSP model, we obtained the broadband color profiles. The theoretical colors match well with the measured colors and present red sharp peaks at the galaxy center. The sharp peaks of the colors are mainly shaped by the high metallicity in the galaxy center. Interestingly, the galaxy has steep negative metallicity gradients, but trend flattens outwards. This result likly suggests that the center and outer regions of the galaxy formed through different formation process.

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“…Here, r e is the effective radius of a galaxy. For a small number of galaxies, mass profiles up to several r e have been obtained using test particles such as globular clusters or planetary nebulae (e.g., Romanowsky et al 2003;Chakrabarty & Raychaudhury 2008).…”

Section: Introductionmentioning

confidence: 99%

Gravitational potential and X-ray luminosities of early-type galaxies observed with XMM-Newton and Chandra

Nagino¹,

Matsushita²

2009

A&A

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Aims. We study the dark matter content in early-type galaxies and investigate whether X-ray luminosities of early-type galaxies are determined by the surrounding gravitational potential. Methods. We derived gravitational mass profiles of 22 early-type galaxies observed with XMM-Newton and Chandra. Results. Sixteen galaxies show constant or decreasing radial temperature profiles, and their X-ray luminosities are consistent with kinematical energy input from stellar mass loss. The temperature profiles of the other 6 galaxies increase with radius, and their X-ray luminosities are significantly higher. The integrated mass-to-light ratio of each galaxy is constant at that of stars within 0.5-1 r e , and increases with radius, where r e is the effective radius of a galaxy. The scatter of the central mass-to-light ratio of galaxies was less in K-band light. At 3 r e , the integrated mass-to-light ratios of galaxies with flat or decreasing temperature profiles are twice the value at 0.5 r e , where the stellar mass dominates, and at 6 r e , these increase to three times the value at 0.5 r e . Conclusions. This feature should reflect common dark and stellar mass distributions in early-type galaxies: within 3 r e , the mass of dark matter is similar to the stellar mass, while within 6 r e , the former is larger than the latter by a factor of two. In contrast, X-ray luminous galaxies have higher gravitational mass in the outer regions than X-ray faint galaxies. We describe these X-ray luminous galaxies as the central objects of large potential structures; the presence or absence of this potential is the main source of the large scatter in the X-ray luminosity.

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The Distribution of Dark Matter in the Halo of the Early-Type Galaxy NGC 4636

Cited by 19 publications

References 43 publications

Comparing X-Ray and Dynamical Mass Profiles in the Early-Type Galaxy NGC 4636

Comparing X-Ray and Dynamical Mass Profiles in the Early-Type Galaxy NGC 4636

Stellar kinematics and populations out to 1.5 effective radii in the elliptical galaxy NGC 4636

Gravitational potential and X-ray luminosities of early-type galaxies observed with XMM-Newton and Chandra

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