scholarly journals Dwarf Cosmology with the Stromlo Missing Satellites Survey

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
Helmut Jerjen
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Primary Objective ◽  
Sloan Digital Sky Survey ◽  
Galaxy Formation And Evolution ◽  
National University ◽  
Formation And Evolution ◽  
Satellite Galaxies

The standard Lambda Cold Dark Matter model is considered to be a triumph of theoretical astrophysics but observations of the Milky Way and its system of satellite galaxies irresistibly signal that theory is incomplete on galactic and subgalactic scales. The Stromlo Missing Satellites (SMS) Survey is a critical endeavor to investigate at what level predictions of CDM cosmology are consistent with the observed matter distribution in the Milky Way halo. It will be the deepest, most extended search for optically elusive satellite galaxies to date, covering 20 000 square degrees of sky. The international SMS Survey collaboration will exploit 150 TB of CCD images in six filters acquired by the new SkyMapper telescope of the Australian National University over the next five years, expecting on completion photometric limits 0.5–1.0 mag fainter than the Sloan Digital Sky Survey. The primary objective of the program is to characterise the baryonic and dark matter components of a complete sample of MW satellites in the Southern hemisphere to provide stringent observational constraints for improving our understanding of how the Milky Way formed and what physical processes governed galaxy formation and evolution in general.

scholarly journals Galaxies on Sub-Galactic Scales

2012 ◽  
Vol 29 (4) ◽  
pp. 383-394 ◽  
Author(s):  
Helmut Jerjen
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Near Field ◽  
Sloan Digital Sky Survey ◽  
Matter Theory ◽  
Satellite Galaxies ◽  
Star Formation Histories

AbstractThe Sloan Digital Sky Survey has been immensely successful in detecting new Milky Way satellite galaxies over the past seven years. It was instrumental in finding examples of the least luminous galaxies we know in the Universe, uncovering apparent inconsistencies between cold dark matter theory and dwarf galaxy properties, providing first evidence for a possible lower mass limit for dark matter halos in visible galaxies, and reopening the discussion about the building block scenario for the Milky Way halo. Nonetheless, these results are still drawn only from a relatively small number of galaxies distributed over an area covering about 29% of the sky, which leaves us currently with more questions than answers. The study of these extreme stellar systems is a multi-parameter problem: ages, metallicities, star formation histories, dark matter contents, population fractions and spatial distributions must be determined. Progress in the field is discussed and attention drawn to some of the limitations that currently hamper our ability to fully understand the phenomenon of the ‘ultra-faint dwarf galaxy’. In this context, the Stromlo Milky Way Satellite Survey represents a new initiative to systematically search and scrutinize optically elusive Milky Way satellite galaxies in the Southern hemisphere. In doing so, the program aims at investigating some of the challenging questions in stellar evolution, galaxy formation and near-field cosmology.

Searching for Ultra-diffuse galaxies in the low-density environment around NGC 3115

2019 ◽  
Vol 15 (S359) ◽  
pp. 257-259
Author(s):  
Marco Canossa-Gosteinski ◽  
Ana L. Chies-Santos ◽  
Cristina Furlanetto ◽  
Rodrigo F. Freitas ◽  
William Schoenell
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Visual Inspection ◽  
Milky Way ◽  
Structural Parameters ◽  
Low Density ◽  
Massive Galaxies ◽  
Galaxy Formation And Evolution ◽  
Formation And Evolution

AbstractUltra-diffuse galaxies (UDGs) are extremely low luminosity galaxies and some of them seem to have a lack of dark matter. Therefore, they can offer important clues to better understand galaxy formation and evolution. Little is known about UDGs in less dense environments, as most of the known UDGs have been found in very dense regions, in the outskirts of massive galaxies in galaxy clusters. In this work, we present the properties of UDGs candidates identified through visual inspection around the low-density environment of NGC 3115, the closest S0 galaxy from the Milky Way. We have measured the structural parameters of 41 UDGs candidates using images obtained with the Dark Energy Camera at the Blanco Telescope. Such structural parameters will be used to characterise and select the best UDG candidates, that will have their properties traced for future follow-up campaigns.

scholarly journals A New Catalog of Isolated Galaxies

2009 ◽  
Vol 5 (S267) ◽  
pp. 464-464
Author(s):  
J. A. Vázquez-Mata ◽  
H. M. Hernández-Toledo ◽  
Changbom Park ◽  
Yun-Young Choi
Keyword(s):  
Galaxy Formation ◽  
Environmental Effects ◽  
Comparative Studies ◽  
Sloan Digital Sky Survey ◽  
Selection Algorithm ◽  
Isolated Galaxies ◽  
Galaxy Formation And Evolution ◽  
Sky Survey ◽  
Data Release ◽  
Formation And Evolution

We present a new catalog of isolated galaxies (coined as UNAM–KIAS) obtained through an automated systematic search. The 1520 isolated galaxies were found in ~ 1.4 steradians of the sky in the Sloan Digital Sky Survey Data Release 5 (SDSS DR5) photometry. The selection algorithm was implemented from a variation of the criteria developed by Karachentseva (1973), with full redshift information. This new catalog is aimed to carry out comparative studies of environmental effects and constraining the currently competing scenarios of galaxy formation and evolution.

scholarly journals Baryonic Dark Halos: a model with MACHOS and cold gas globules

1996 ◽  
Vol 171 ◽  
pp. 167-170
Author(s):  
Ortwin Gerhard ◽  
Joseph Silk
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Active Role ◽  
Galaxy Formation And Evolution ◽  
Substellar Objects ◽  
Formation And Evolution ◽  
Cold Gas

The dark matter in the halos of galaxies may well be baryonic, and much of the mass within them could be in the form of clusters of substellar objects within which are embedded cold gas globules. Such halos might play an active role in galaxy formation and evolution.

scholarly journals Heating of Milky Way disc stars by dark matter fluctuations in cold dark matter and fuzzy dark matter paradigms

2019 ◽  
Vol 485 (2) ◽  
pp. 2861-2876 ◽  
Author(s):  
Benjamin V Church ◽  
Philip Mocz ◽  
Jeremiah P Ostriker
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Quantum Interference ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Formation Rate ◽  
Density Fluctuations ◽  
Particle Mass ◽  
Small Scale

ABSTRACT Although highly successful on cosmological scales, cold dark matter (CDM) models predict unobserved overdense ‘cusps’ in dwarf galaxies and overestimate their formation rate. We consider an ultralight axion-like scalar boson which promises to reduce these observational discrepancies at galactic scales. The model, known as fuzzy dark matter (FDM), avoids cusps, suppresses small-scale power, and delays galaxy formation via macroscopic quantum pressure. We compare the substructure and density fluctuations of galactic dark matter haloes comprised of ultralight axions to conventional CDM results. Besides self-gravitating subhaloes, FDM includes non-virialized overdense wavelets formed by quantum interference patterns, which are an efficient source of heating to galactic discs. We find that, in the solar neighbourhood, wavelet heating is sufficient to give the oldest disc stars a velocity dispersion of ${\sim } {30}{\, \mathrm{km\, s}^{-1}}$ within a Hubble time if energy is not lost from the disc, the velocity dispersion increasing with stellar age as σD ∝ t0.4 in agreement with observations. Furthermore, we calculate the radius-dependent velocity dispersion and corresponding scaleheight caused by the heating of this dynamical substructure in both CDM and FDM with the determination that these effects will produce a flaring that terminates the Milky Way disc at $15\!-\!20{\, \mathrm{kpc}}$. Although the source of thickened discs is not known, the heating due to perturbations caused by dark substructure cannot exceed the total disc velocity dispersion. Therefore, this work provides a lower bound on the FDM particle mass of ma > 0.6 × 10−22 eV. Furthermore, FDM wavelets with this particle mass should be considered a viable mechanism for producing the observed disc thickening with time.

scholarly journals How dark are filaments in the cosmic web?

2020 ◽  
Vol 498 (3) ◽  
pp. 3158-3170
Author(s):  
Tianyi Yang ◽  
Michael J Hudson ◽  
Niayesh Afshordi
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Weak Lensing ◽  
Sky Survey ◽  
Mass Fractions ◽  
The Masses ◽  
Red Galaxies

ABSTRACT The cold dark matter model predicts that dark matter haloes are connected by filaments. Direct measurements of the masses and structure of these filaments are difficult, but recently several studies have detected these dark-matter-dominated filaments using weak lensing. Here we study the efficiency of galaxy formation within the filaments by measuring their total mass-to-light ratios and stellar mass fractions. Specifically, we stack pairs of luminous red galaxies (LRGs) with a typical separation on the sky of 8 h−1 Mpc. We stack background galaxy shapes around pairs to obtain mass maps through weak lensing, and we stack galaxies from the Sloan Digital Sky Survey to obtain maps of light and stellar mass. To isolate the signal from the filament, we construct two matched catalogues of physical and non-physical (projected) LRG pairs, with the same distributions of redshift and separation. We then subtract the two stacked maps. Using LRG pair samples from the Baryon Oscillation Spectroscopic Survey at two different redshifts, we find that the evolution of the mass in filament is consistent with the predictions from perturbation theory. The filaments are not entirely dark: Their mass-to-light ratios (M/L = 351 ± 137 in solar units in the rband) and stellar mass fractions (Mstellar/M = 0.0073 ± 0.0030) are consistent with the cosmic values (and with their redshift evolutions).

THE LINK BETWEEN GALAXIES AND DARK MATTER

2011 ◽  
Vol 20 (10) ◽  
pp. 1771-1777
Author(s):  
HOUJUN MO
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Luminosity Function ◽  
The Other ◽  
Dark Matter Halos ◽  
Galaxy Formation And Evolution ◽  
The Galaxy ◽  
Galaxy Halo ◽  
Formation And Evolution ◽  
The Universe

Given that dark matter is gravitationally dominant in the universe, and that galaxy formation is closely related to dark matter halos, a key first step in understanding galaxy formation and evolution in the CDM paradigm is to quantify the galaxy-halo connection for galaxies of different properties. Here I will present results about the halo/galaxy connection obtained from two different methods. One is based on the conditional luminosity function, which describes the occupation of galaxies in halos of different masses, and the other is based on galaxy systems properly selected to represent dark halos.

scholarly journals Stellar migrations and metal flows – Chemical evolution of the thin disc of a simulated Milky Way analogous galaxy

2020 ◽  
Vol 496 (1) ◽  
pp. 80-94 ◽  
Author(s):  
Fiorenzo Vincenzo ◽  
Chiaki Kobayashi
Keyword(s):  
Galaxy Formation ◽  
Milky Way ◽  
Formation Rate ◽  
Age Distribution ◽  
Radial Dependence ◽  
Radial Gradient ◽  
Thin Disc ◽  
Galaxy Formation And Evolution ◽  
Age Relation ◽  
Formation And Evolution

ABSTRACT In order to understand the roles of metal flows in galaxy formation and evolution, we analyse our self-consistent cosmological chemodynamical simulation of a Milky Way like galaxy during its thin-disc phase. Our simulated galaxy disc qualitatively reproduces the variation of the dichotomy in [α/Fe]–[Fe/H] at different Galactocentric distances as derived by APOGEE-DR16, as well as the stellar age distribution in [α/Fe]–[Fe/H] from APOKASC-2. The disc grows from the inside out, with a radial gradient in the star-formation rate during the entire phase. Despite the radial dependence, the outflow-to-infall ratio of metals in our simulated halo shows a time-independent profile scaling with the disc growth. The simulated disc undergoes two modes of gas inflow: (i) an infall of metal-poor and relatively low-[α/Fe] gas, and (ii) a radial flow where already chemically enriched gas moves inwards with an average velocity of ∼0.7 km s−1. Moreover, we find that stellar migrations mostly happen outwards, on typical time-scales of ∼5 Gyr. Our predicted radial metallicity gradients agree with the observations from APOGEE-DR16, and the main effect of stellar migrations is to flatten the radial metallicity profiles by 0.05 dex/kpc in the slopes. We also show that the effect of migrations can appear more important in [α/Fe] than in the [Fe/H]–age relation of thin-disc stars.

scholarly journals A dark matter profile to model diverse feedback-induced core sizes of ΛCDM haloes

2020 ◽  
Vol 497 (2) ◽  
pp. 2393-2417 ◽  
Author(s):  
Alexandres Lazar ◽  
James S Bullock ◽  
Michael Boylan-Kolchin ◽  
T K Chan ◽  
Philip F Hopkins ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Dark Matter Halo ◽  
Constant Density ◽  
Core Formation ◽  
Density Profiles ◽  
The Galaxy ◽  
Two Parameter

ABSTRACT We analyse the cold dark matter density profiles of 54 galaxy haloes simulated with Feedback In Realistic Environments (FIRE)-2 galaxy formation physics, each resolved within $0.5{{\ \rm per\ cent}}$ of the halo virial radius. These haloes contain galaxies with masses that range from ultrafaint dwarfs ($M_\star \simeq 10^{4.5}\, \mathrm{M}_{\odot }$) to the largest spirals ($M_\star \simeq 10^{11}\, \mathrm{M}_{\odot }$) and have density profiles that are both cored and cuspy. We characterize our results using a new, analytic density profile that extends the standard two-parameter Einasto form to allow for a pronounced constant density core in the resolved innermost radius. With one additional core-radius parameter, rc, this three-parameter core-Einasto profile is able to characterize our feedback-impacted dark matter haloes more accurately than other three-parameter profiles proposed in the literature. To enable comparisons with observations, we provide fitting functions for rc and other profile parameters as a function of both M⋆ and M⋆/Mhalo. In agreement with past studies, we find that dark matter core formation is most efficient at the characteristic stellar-to-halo mass ratio M⋆/Mhalo ≃ 5 × 10−3, or $M_{\star } \sim 10^9 \, \mathrm{M}_{\odot }$, with cores that are roughly the size of the galaxy half-light radius, rc ≃ 1−5 kpc. Furthermore, we find no evidence for core formation at radii $\gtrsim 100\ \rm pc$ in galaxies with M⋆/Mhalo < 5 × 10−4 or $M_\star \lesssim 10^6 \, \mathrm{M}_{\odot }$. For Milky Way-size galaxies, baryonic contraction often makes haloes significantly more concentrated and dense at the stellar half-light radius than DMO runs. However, even at the Milky Way scale, FIRE-2 galaxy formation still produces small dark matter cores of ≃ 0.5−2 kpc in size. Recent evidence for a ∼2 kpc core in the Milky Way’s dark matter halo is consistent with this expectation.

scholarly journals Characterisation of the Galactic thick disk

2013 ◽  
Vol 9 (S298) ◽  
pp. 17-27
Author(s):  
Thomas Bensby
Keyword(s):  
Galaxy Formation ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Thin Disk ◽  
Thick Disk ◽  
Host Galaxy ◽  
Galaxy Formation And Evolution ◽  
Formation History ◽  
History Of ◽  
Formation And Evolution

AbstractThick disks appear to be common in external large spiral galaxies and our own Milky Way also hosts one. The existence of a thick disk is possibly directly linked to the formation history of the host galaxy and if its properties is known it can constrain models of galaxy formation and help us to better understand galaxy formation and evolution. This brief review attempts to highlight some of the characteristics of the Galactic thick disk and how it relates to other stellar populations such as the thin disk and the Galactic bulge. Focus has been put on results from high-resolution spectroscopic data obtained during the last 10 to 15 years.

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