scholarly journals THE STELLAR DENSITY PROFILE OF THE DISTANT GALACTIC HALO

2016 ◽  
Vol 832 (2) ◽  
pp. 206 ◽  
Author(s):  
Colin T. Slater ◽  
David L. Nidever ◽  
Jeffrey A. Munn ◽  
Eric F. Bell ◽  
Steven R. Majewski
Keyword(s):  
Density Profile ◽  
Galactic Halo ◽  
Stellar Density

scholarly journals Hubble Space Telescope Studies of the Dense Central Regions of Globular Clusters

1996 ◽  
Vol 174 ◽  
pp. 19-28
Author(s):  
Puragra Guhathakurta ◽  
Brian Yanny ◽  
Donald P. Schneider ◽  
John N. Bahcall
Keyword(s):  
Density Profile ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Core Collapse ◽  
Red Giants ◽  
Space Telescope ◽  
Blue Straggler ◽  
Central Regions ◽  
Stellar Density

We present results from an ongoing program to probe the dense central parts of Galactic globular clusters using multicolor Hubble Space Telescope images (WF/PC-I and WFPC2). Our sample includes the dense clusters M15, 47 Tuc, M30, NGC 6624, M3 and M13. The two main goals of our program are to measure the shape of stellar density profile in clusters (the slope of the density cusp in post core collapse clusters, in particular) and to understand the nature of evolved stellar populations in very dense regions and their variation as a function of radius. The latter includes studies of blue straggler stars and of the central depletion of bright red giants. Our recent WFPC2 study of M15 is described in detail.

Existence of wormhole supported by the Einasto density profile

2018 ◽  
Vol 96 (11) ◽  
pp. 1242-1245
Author(s):  
Banashree Sen
Keyword(s):  
Density Profile ◽  
Galactic Halo ◽  
Rotational Velocity ◽  
Space Time ◽  
Velocity Curve ◽  
Density Model ◽  
Degree Polynomial ◽  
Traversable Wormhole

In this article, the existence of traversable wormhole in the outer and inner regions of the halos of galaxies using Einasto density profile has been investigated. We use Einasto density model, which is a 3D version of 2D Sérsic model (Dhar and Williams. M. Not. R. Astron. Soc. 405, 340 (2010). doi: 10.1111/j.1365-2966.2010.16446.x ). Two types of rotational velocity curve (one is a fifth degree polynomial and another is a constant) derived from experimental or observed data have been taken into account for describing the space–time of galactic halo comprising a traversable wormhole.

scholarly journals Direct Mapping of Massive Compact Objects in Extragalactic Dark Halos

2004 ◽  
Vol 220 ◽  
pp. 139-140
Author(s):  
Kaiki Taro Inoue ◽  
Masashi Chiba
Keyword(s):  
Spatial Distribution ◽  
High Resolution ◽  
Density Profile ◽  
Gravitational Lensing ◽  
Galactic Halo ◽  
Compact Objects ◽  
Multiple Images ◽  
Direct Mapping ◽  
Radio Map

We propose a method for directly detecting MASsive Compact Objects (MASCOs) in extragalactic halos, using VLBI techniques with extremely high resolution ˜ 0.01 milli-arcsec. If a galactic halo comprising a large number of MASCOs produces multiple images of a background radio-loud QSO by gravitational lensing, then a high-resolution radio map of each macro-lensed image should reveal microlensing effects by MASCOs. Based on the size, position, and magnified or demagnified patterns of images, we shall be able to determine the mass and density profile of an individual MASCO as well as its spatial distribution and abundance in a galactic halo.

scholarly journals The radial velocity dispersion profile of the Galactic halo: constraining the density profile of the dark halo of the Milky Way

2005 ◽  
Vol 364 (2) ◽  
pp. 433-442 ◽  
Author(s):  
Giuseppina Battaglia ◽  
Amina Helmi ◽  
Heather Morrison ◽  
Paul Harding ◽  
Edward W. Olszewski ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Density Profile ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Galactic Halo ◽  
Dark Halo ◽  
Dispersion Profile

scholarly journals The Galactic halo stellar density distribution from photometric survey data: results of a pilot study

2006 ◽  
Vol 463 (3) ◽  
pp. 975-979 ◽  
Author(s):  
M. Cignoni ◽  
V. Ripepi ◽  
M. Marconi ◽  
J. M. Alcalá ◽  
M. Capaccioli ◽  
...  
Keyword(s):  
Pilot Study ◽  
Density Distribution ◽  
Survey Data ◽  
Galactic Halo ◽  
Stellar Density

scholarly journals The total stellar halo mass of the Milky Way

2019 ◽  
Vol 490 (3) ◽  
pp. 3426-3439 ◽  
Author(s):  
Alis J Deason ◽  
Vasily Belokurov ◽  
Jason L Sanders
Keyword(s):  
Density Profile ◽  
Galactic Halo ◽  
Mass Function ◽  
Initial Mass Function ◽  
Total Luminosity ◽  
Stellar Halo ◽  
Merger Event ◽  
Red Giant ◽  
Number Counts ◽  
Good Agreement

ABSTRACT We measure the total stellar halo luminosity using red giant branch (RGB) stars selected from Gaia data release 2. Using slices in magnitude, colour, and location on the sky, we decompose RGB stars belonging to the disc and halo by fitting two-dimensional Gaussians to the Galactic proper motion distributions. The number counts of RGB stars are converted to total stellar halo luminosity using a suite of isochrones weighted by age and metallicity, and by applying a volume correction based on the stellar halo density profile. Our method is tested and calibrated using Galaxia and N-body models. We find a total luminosity (out to 100 kpc) of $L_{\rm halo} = 7.9 \pm 2.0 \times 10^8\, \mathrm{L}_\odot$ excluding Sgr, and $L_{\rm halo} = 9.4 \pm 2.4 \times 10^8\, \mathrm{L}_\odot$ including Sgr. These values are appropriate for our adopted stellar halo density profile and metallicity distribution, but additional systematics related to these assumptions are quantified and discussed. Assuming a stellar mass-to-light ratio appropriate for a Kroupa initial mass function (M⋆/L = 1.5), we estimate a stellar halo mass of $M^\star _{\rm halo} = 1.4 \pm 0.4\times 10^9 \, \mathrm{M}_\odot$. This mass is larger than previous estimates in the literature, but is in good agreement with the emerging picture that the (inner) stellar halo is dominated by one massive dwarf progenitor. Finally, we argue that the combination of a ${\sim}10^9\, \mathrm{M}_\odot$ mass and an average metallicity of 〈[Fe/H]〉 ∼ −1.5 for the Galactic halo points to an ancient (∼10 Gyr) merger event.

scholarly journals A robust two-parameter description of the stellar profile of elliptical galaxies

2020 ◽  
Vol 641 ◽  
pp. A143
Author(s):  
Alessandro Sonnenfeld
Keyword(s):  
Density Profile ◽  
Velocity Dispersion ◽  
Finite Depth ◽  
Elliptical Galaxies ◽  
Stellar Mass ◽  
The Galaxy ◽  
Stellar Velocity ◽  
Hydrodynamical Simulations ◽  
Two Parameter ◽  
Stellar Density

Context. The stellar density profile of a galaxy is typically summarised with two numbers: the total stellar mass and half-light radius. The total mass of a galaxy, however, is not a well-defined quantity, due to the finite depth of photometric observations and the arbitrariness of the distinction between galaxy and diffuse intra-group light. This limits our ability to make accurate comparisons between models and observations. Aims. I wish to provide a more robust two-parameter description of the stellar density distribution of elliptical galaxies, in terms of quantities that can be measured unambiguously. Methods. I propose using the stellar mass enclosed within 10 kpc in projection, M*,10, and the mass-weighted stellar density slope within the same aperture, Γ*,10, for this purpose. I measured the distribution in M*,10 and Γ*,10 of a sample of elliptical galaxies from the Sloan Digital Sky Survey and the Galaxy And Mass Assembly survey, using photometry from the Hyper Suprime-Cam survey. I measured, at fixed (M*,10, Γ*,10), what the spread is in the galaxy surface brightness profile and central stellar velocity dispersion within the sample. As a first application, I then compared the observed M*,10 − Γ*,10 relation of elliptical galaxies with that of similarly selected galaxies in the EAGLE REFERENCE simulation. Results. The pair of values of (M*,10, Γ*,10) can be used to predict the stellar density profile in the inner 10 kpc of a galaxy with better than 20% accuracy. Similarly, M*,10 and Γ*,10 can be combined to obtain a proxy for stellar velocity dispersion that is at least as good as the stellar mass fundamental plane. The average stellar density slope of EAGLE elliptical galaxies matches that of observed ones at M*,10 = 1011 M⊙ well, but the EAGLE M*,10 − Γ*,10 relation is shallower and has a larger intrinsic scatter compared to observations. Conclusions. This new parameterisation of the stellar density profile of massive elliptical galaxies provides a more robust way of comparing results from different photometric surveys and from hydrodynamical simulations, with respect to a description based on total stellar mass and half-light radius.

scholarly journals Stellar density profile and mass of the Milky Way bulge from VVV data

2016 ◽  
Vol 587 ◽  
pp. L6 ◽  
Author(s):  
E. Valenti ◽  
M. Zoccali ◽  
O. A. Gonzalez ◽  
D. Minniti ◽  
J. Alonso-García ◽  
...  
Keyword(s):  
Density Profile ◽  
Milky Way ◽  
Stellar Density

scholarly journals Origin and Ionization of the Warm Ionized Gas in Massive Early-type Galaxies

2012 ◽  
Vol 8 (S295) ◽  
pp. 328-331
Author(s):  
Renbin Yan ◽  
Michael R. Blanton
Keyword(s):  
Emission Line ◽  
Gas Phase ◽  
Density Profile ◽  
Line Emission ◽  
Ionization Mechanism ◽  
Early Type ◽  
Ionized Gas ◽  
Present Evidence ◽  
Evolved Stars ◽  
Stellar Density

AbstractMost early-type galaxies are not devoid of cold and warm gas. The origin and ionization of this gas reveal the intriguing ongoing evolution of these galaxies. In most cases, the warm ionized gas shows emission-line spectra similar to low-ionization nuclear emission-line regions (LINERs). Their ionization mechanism has been hotly debated. We will present evidence from line ratio gradient that rules out AGN and shocks as the dominant ionization mechanism, and suggests the ionizing sources follow the stellar density profile. Hot evolved stars are the favorite candidates but bring new puzzles.This finding allows us to obtain a gas-phase metallicity calibration in these early-type galaxies, using the line emission. We will show how the metallicity of the warm gas depends on stellar mass and stellar age, and what it tells us about the origin of the warm gas in these galaxies.

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