scholarly journals The Structural and Kinematic Evolution of Central Star Clusters in Dwarf Galaxies and Their Dependence on Dark Matter Halo Profiles

2018 ◽  
Vol 479 (3) ◽  
pp. 3708-3714 ◽  
Author(s):  
Jeremy J Webb ◽  
Enrico Vesperini
Keyword(s):  
Dark Matter ◽  
Dwarf Galaxies ◽  
Star Clusters ◽  
Central Star ◽  
Dark Matter Halo ◽  
Kinematic Evolution

scholarly journals Bulge Formation from Super Star Clusters in a Responding Cuspy Dark Matter Halo

2007 ◽  
Vol 662 (1) ◽  
pp. 250-258
Author(s):  
Yan‐Ning Fu ◽  
Wen‐Hao Liu ◽  
Jie‐Hao Huang ◽  
Zu‐Gan Deng
Keyword(s):  
Dark Matter ◽  
Star Clusters ◽  
Dark Matter Halo ◽  
Super Star Clusters ◽  
Bulge Formation

scholarly journals Dark Matter in Dwarf Galaxies: High Resolution Observations

2004 ◽  
Vol 220 ◽  
pp. 353-358 ◽  
Author(s):  
Alberto D. Bolatto ◽  
Joshua D. Simon ◽  
Adam Leroy ◽  
Leo Blitz
Keyword(s):  
Dark Matter ◽  
High Resolution ◽  
Rotation Curve ◽  
Dwarf Galaxies ◽  
Full Range ◽  
Dark Matter Halo ◽  
Central Density ◽  
Constant Density ◽  
Density Profiles ◽  
Central Regions

We present observations and analysis of rotation curves and dark matter halo density profiles in the central regions of four nearby dwarf galaxies. This observing program has been designed to overcome some of the limitations of other rotation curve studies that rely mostly on longslit spectra. We find that these objects exhibit the full range of central density profiles between ρ ∝ r0 (constant density) and ρ ∝ r–1 (NFW halo). This result suggests that there is a distribution of central density slopes rather than a unique halo density profile.

scholarly journals Substructure in Dwarf Galaxies

2004 ◽  
Vol 21 (4) ◽  
pp. 379-381
Author(s):  
Matthew Coleman
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Large Scale ◽  
Stellar Population ◽  
Milky Way ◽  
Dwarf Galaxies ◽  
Tidal Interaction ◽  
Kinematic Evolution ◽  
Dark Material ◽  
Star Formation Histories

AbstractRecent years have seen a series of large-scale photometric surveys with the aim of detecting substructure in nearby dwarf galaxies. Some of these objects display a varying distribution of each stellar population, reflecting their star formation histories. Also, dwarf galaxies are dominated by dark matter, therefore luminous substructure may represent a perturbation in the underlying dark material. Substructure can also be the effect of tidal interaction, such as the disruption of the Sagittarius dSph by the Milky Way. Therefore, substructure in dwarf galaxies manifests the stellar, structural, and kinematic evolution of these objects.

scholarly journals Globular clusters as probes of dark matter cusp-core transformations

2019 ◽  
Vol 488 (3) ◽  
pp. 2977-2988 ◽  
Author(s):  
M D A Orkney ◽  
J I Read ◽  
J A Petts ◽  
M Gieles
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
Massive Star ◽  
Dwarf Galaxies ◽  
Dynamical Evolution ◽  
Dark Matter Halo ◽  
Constant Density ◽  
Ngc 6822 ◽  
Hubble Time

Abstract Bursty star formation in dwarf galaxies can slowly transform a steep dark matter cusp into a constant density core. We explore the possibility that globular clusters (GCs) retain a dynamical memory of this transformation. To test this, we use the nbody6df code to simulate the dynamical evolution of GCs, including stellar evolution, orbiting in static and time-varying potentials for a Hubble time. We find that GCs orbiting within a cored dark matter halo, or within a halo that has undergone a cusp-core transformation, grow to a size that is substantially larger (Reff > 10 pc) than those in a static cusped dark matter halo. They also produce much less tidal debris. We find that the cleanest signal of an historic cusp-core transformation is the presence of large GCs with tidal debris. However, the effect is small and will be challenging to observe in real galaxies. Finally, we qualitatively compare our simulated GCs with the observed GC populations in the Fornax, NGC 6822, IKN, and Sagittarius dwarf galaxies. We find that the GCs in these dwarf galaxies are systematically larger (〈Reff〉 ≃ 7.8 pc), and have substantially more scatter in their sizes than in situ metal-rich GCs in the Milky Way and young massive star clusters forming in M83 (〈Reff〉 ≃ 2.5 pc). We show that the size, scatter, and survival of GCs in dwarf galaxies are all consistent with them having evolved in a constant density core, or a potential that has undergone a cusp-core transformation, but not in a dark matter cusp.

scholarly journals Tidal dwarf galaxies as laboratories of star formation and cosmology

2006 ◽  
Vol 2 (S237) ◽  
pp. 323-330 ◽  
Author(s):  
Pierre-Alain Duc ◽  
Frédéric Bournaud ◽  
Médéric Boquien
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Numerical Simulations ◽  
Dwarf Galaxies ◽  
Star Clusters ◽  
Dense Core ◽  
Multi Wavelength ◽  
Interacting Systems ◽  
Super Star Clusters ◽  
Tidal Tails

AbstractStar formation may take place in a variety of locations in interacting systems: in the dense core of mergers, in the shock regions at the interface of the colliding galaxies and even within the tidal debris expelled into the intergalactic medium. Along tidal tails, objects may be formed with masses ranging from those of super-star clusters to dwarf galaxies: the so-called Tidal Dwarf Galaxies (TDGs). Based on a set of multi-wavelength observations and extensive numerical simulations, we show how TDGs may simultaneously be used as laboratories to study the process of star-formation (SFE, IMF) in a specific environment and as probes of various cosmological properties, such as the distribution of dark matter and satellites around galaxies.

scholarly journals Chemical evolution of star clusters

2010 ◽  
Vol 368 (1913) ◽  
pp. 801-828 ◽  
Author(s):  
Jacco Th. van Loon
Keyword(s):  
Dark Matter ◽  
Chemical Evolution ◽  
Gravitational Potential ◽  
Globular Clusters ◽  
Galactic Halo ◽  
Dwarf Galaxies ◽  
Star Clusters ◽  
Galactic Bulge ◽  
Potential Wells ◽  
The Galaxy

I discuss the chemical evolution of star clusters, with emphasis on old Galactic globular clusters (GCs), in relation to their formation histories. GCs are clearly formed in a complex fashion, under markedly different conditions from any younger clusters presently known. Those special conditions must be linked to the early formation epoch of the Galaxy and must not have occurred since. While a link to the formation of GCs in dwarf galaxies has been suggested, present-day dwarf galaxies are not representative of the gravitational potential wells within which the GCs formed. Instead, a formation deep within the proto-Galaxy or within dark-matter mini-haloes might be favoured. Not all GCs may have formed and evolved similarly. In particular, we may need to distinguish Galactic Halo from Galactic Bulge clusters.

scholarly journals Influence of the Void Environment on Chemical Abundances in Dwarf Galaxies and Implications for Connecting Star Formation and Halo Mass

2018 ◽  
Vol 14 (S344) ◽  
pp. 369-372
Author(s):  
Kelly A. Douglass ◽  
Michael S. Vogeley ◽  
Renyue Cen
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Large Scale ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Direct Method ◽  
Dark Matter Halo ◽  
Chemical Abundances ◽  
Abundance Estimates ◽  
Galaxy Populations

AbstractWe study how the void environment affects the chemical evolution of galaxies by comparing the metallicity of dwarf galaxies in voids with dwarf galaxies in denser regions. Using spectroscopic observations from SDSS DR7, we estimate oxygen and nitrogen abundances of 889 void dwarf galaxies and 672 dwarf galaxies in denser regions. A substitute for the [OII] λ3727 doublet is developed, permitting oxygen abundance estimates of SDSS dwarf galaxies at all redshifts with the direct method. We find that void dwarf galaxies have about the same oxygen abundances and slightly lower N/O ratios than dwarf galaxies in denser environments. The lower N/O ratios seen in void dwarf galaxies may indicate both delayed star formation and a dependence of cosmic downsizing on the large-scale environment. Similar oxygen abundances in the two dwarf galaxy populations might be evidence of larger ratios of dark matter halo mass to stellar mass in voids.

scholarly journals Ghostly haloes in dwarf galaxies: constraints on the star formation efficiency before reionization

2019 ◽  
Vol 488 (2) ◽  
pp. 2673-2688
Author(s):  
Hoyoung D Kang ◽  
Massimo Ricotti
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Dwarf Galaxies ◽  
Mass Range ◽  
Small Mass ◽  
Dark Matter Halo ◽  
Host Galaxy ◽  
Normal Galaxies ◽  
Stellar Halo ◽  
Formation Efficiency

ABSTRACT Stellar haloes observed around normal galaxies are extended and faint stellar structures formed by debris of tidally disrupted dwarf galaxies accreted overtime by the host galaxy. Around dwarf galaxies, these stellar haloes may not exist if all the accreted satellites are dark haloes without stars. However, if a stellar halo is found in sufficiently small mass dwarfs, the whole stellar halo is composed of tidal debris of fossil galaxies, and we refer to it as ghostly halo. Fossil galaxies are so called because they formed most of their stars before the epoch of reionization, and have been identified as the ultrafaint dwarf galaxies found around the Milky Way and M31. In this paper, we carry out semi-analytical simulations to characterize the sizes and stellar masses of ghostly stellar haloes in dwarf galaxies as a function of their dark matter halo mass. By comparing the models to observations of six isolated dwarf galaxies in the Local Group showing evidence of extended stellar haloes, we are able to constrain the star formation efficiency in fossil galaxies. We find that at redshift z ∼ 6, dark matter haloes in the mass range 107–109 M⊙ have a mean star formation efficiency $f_* \equiv M_*/M_{\mathrm{ dm}} \sim 0.1\!-\!0.2\hbox{ per cent}$ nearly constant as a function of the dark matter halo mass.

scholarly journals Mass models of gas-rich void dwarf galaxies

2019 ◽  
Vol 491 (4) ◽  
pp. 4993-5014 ◽  
Author(s):  
Sushma Kurapati ◽  
Jayaram N Chengalur ◽  
Peter Kamphuis ◽  
Simon Pustilnik
Keyword(s):  
Dark Matter ◽  
Dwarf Galaxies ◽  
Matter Density ◽  
Field Analysis ◽  
Dark Matter Halo ◽  
Normal Density ◽  
Density Profiles ◽  
Dark Matter Density ◽  
Average Slope ◽  
Systematic Effects

ABSTRACT We construct mass models of eight gas rich dwarf galaxies that lie in the Lynx–Cancer void. From NFW fits to the dark matter halo profile, we find that the concentration parameters of haloes of void dwarf galaxies are similar to those of dwarf galaxies in normal density regions. We also measure the slope of the central dark matter density profiles, obtained by converting the rotation curves derived using 3D (fat) and 2D (ROTCUR) tilted ring fitting routines, into mass densities. We find that the average slope (α = −1.39 ± 0.19), obtained from 3D fitting is consistent with that expected from an NFW profile. On the other hand, the average slope measured using the 2D approach is closer to what would be expected for an isothermal profile. This suggests that systematic effects in velocity field analysis have a significant effect on the slope of the central dark matter density profiles. Given the modest number of galaxies we use for our analysis, it is important to check these results using a larger sample.

scholarly journals Voids in the Local Volume: a Limit on Appearance of a Galaxy in a Dark Matter Halo

2007 ◽  
Vol 3 (S244) ◽  
pp. 152-156
Author(s):  
Anton V. Tikhonov ◽  
Anatoly A. Klypin
Keyword(s):  
Dark Matter ◽  
High Resolution ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Dark Matter Halo ◽  
Dark Matter Halos ◽  
Host Galaxies ◽  
Group Data ◽  
Luminous Matter ◽  
Very High

AbstractCurrent explanation of the overabundance of dark matter subhalos in the Local Group (LG) indicates that there maybe a limit on mass of a halo, which can host a galaxy. This idea can be tested using voids in the distribution of galaxies: at some level small voids should not contain any (even dwarf) galaxies. We use observational samples complete to MB = −12 with distances less than 8 Mpc to construct the void function (VF): the distribution of sizes of voids empty of any galaxies. There are ~ 30 voids with sizes ranging from 1 to 5 Mpc. We then study the distribution of dark matter halos in very high resolution simulations of the LCDM model. The theoretical VF matches the observations remarkably well only if we use halos with circular velocities larger than 45 ± 10 km/s. This agrees with the Local Group predictions. There are smaller halos in the voids, but they should not produce any luminous matter. Small voids look quite similar to their giant cousins: the density has a minimum at the center of a void and it increases as we get closer to the border. Small nonluminous halos inside the void form a web of tiny filaments. Thus, both the Local Group data and the nearby voids indicate that isolated halos below 45 ± 10 km/s must not host galaxies and that small (few Mpc) voids are truly dark.

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