scholarly journals The Faint Globular Cluster in the Dwarf Galaxy Andromeda I

2017 ◽  
Vol 34 ◽  
Author(s):  
Nelson Caldwell ◽  
Jay Strader ◽  
David J. Sand ◽  
Beth Willman ◽  
Anil C. Seth
Keyword(s):  
Dark Matter ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Dark Matter Halos ◽  
History Of ◽  
Low Mass ◽  
Growing Population

AbstractObservations of globular clusters in dwarf galaxies can be used to study a variety of topics, including the structure of dark matter halos and the history of vigorous star formation in low-mass galaxies. We report on the properties of the faint globular cluster (MV ~ −3.4) in the M31 dwarf galaxy Andromeda I. This object adds to the growing population of low-luminosity Local Group galaxies that host single globular clusters.

scholarly journals Evolution of C iv Absorbers. II. Where Does C iv Live?

2022 ◽  
Vol 924 (1) ◽  
pp. 12
Author(s):  
Farhanul Hasan ◽  
Christopher W. Churchill ◽  
Bryson Stemock ◽  
Nikole M. Nielsen ◽  
Glenn G. Kacprzak ◽  
...  
Keyword(s):  
Dark Matter ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Dark Matter Halos ◽  
Lower Mass ◽  
Massive Galaxies ◽  
Galaxy Halos ◽  
Low Mass ◽  
Galaxy Halo ◽  
Halo Gas

Abstract We use the observed cumulative statistics of C iv absorbers and dark matter halos to infer the distribution of C iv-absorbing gas relative to galaxies at redshifts 0 ≤ z ≤ 5. We compare the cosmic incidence dN/dX of C iv absorber populations and galaxy halos, finding that massive L ≥ L ⋆ halos alone cannot account for all the observed W r ≥ 0.05 Å absorbers. However, the dN/dX of lower-mass halos exceeds that of W r ≥ 0.05 Å absorbers. We also estimate the characteristic gas radius of absorbing structures required for the observed C iv dN/dX, assuming each absorber is associated with a single galaxy halo. The W r ≥ 0.3 Å and W r ≥ 0.6 Å C iv gas radii are ∼30%–70% (∼20%–40%) of the virial radius of L ⋆ (0.1L ⋆) galaxies, and the W r ≥ 0.05 Å gas radius is ∼100%–150% (∼60%–100%) of the virial radius of L ⋆ (0.1L ⋆) galaxies. For stronger absorbers, the gas radius relative to the virial radius rises across Cosmic Noon and falls afterwards, while for weaker absorbers, the relative gas radius declines across Cosmic Noon and then dramatically rises at z < 1. A strong luminosity-dependence of the gas radius implies highly extended C iv envelopes around massive galaxies before Cosmic Noon, while a luminosity-independent gas radius implies highly extended envelopes around dwarf galaxies after Cosmic Noon. From available absorber-galaxy and C iv evolution data, we favor a scenario in which low-mass galaxies enrich the volume around massive galaxies at early epochs and propose that the outer halo gas (>0.5 R v ) was produced primarily in ancient satellite dwarf galaxy outflows, while the inner halo gas (<0.5 R v ) originated from the central galaxy and persists as recycled accreting gas.

scholarly journals In Pursuit of the Least Luminous Galaxies

2010 ◽  
Vol 2010 ◽  
pp. 1-11 ◽  
Author(s):  
Beth Willman
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Field Survey ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Wide Field ◽  
Dark Matter Halos ◽  
The Past ◽  
Luminous Galaxies ◽  
Host Stars

The dwarf galaxy companions to the Milky Way are unique cosmological laboratories. With luminosities as low as10−7LMW, they inhabit the lowest mass dark matter halos known to host stars and are presently the most direct tracers of the distribution, mass spectrum, and clustering scale of dark matter. Their resolved stellar populations also facilitate detailed studies of their history and mass content. To fully exploit this potential requires a well-defined census of virtually invisible galaxies to the faintest possible limits and to the largest possible distances. I review the past and present impacts of survey astronomy on the census of Milky Way dwarf galaxy companions and discuss the future of finding ultra-faint dwarf galaxies around the Milky Way and beyond in wide-field survey data.

Isolated dwarf galaxies in the Local Group

2018 ◽  
Vol 14 (S344) ◽  
pp. 81-85
Author(s):  
Clare R. Higgs ◽  
Alan W. McConnachie ◽  
Keyword(s):  
Globular Clusters ◽  
Local Group ◽  
Dwarf Galaxy ◽  
Apparent Size ◽  
Stellar Structure ◽  
Star Formation History ◽  
Wide Field ◽  
Formation History ◽  
Close Proximity ◽  
Low Mass

AbstractThe Solo (Solitary local) Dwarf Galaxy Survey is a volume limited sample of all nearby (< 3 Mpc) and isolated (> 300 kpc from the Milky Way or M31) dwarfs, with wide-field g and i imaging. This survey uses resolved stellar populations to parameterize these low mass systems. Comparison to the well studied satellite dwarfs characterizes the evolutionary impact of a large galaxy in close proximity. The deep, wide field nature of this survey also lends itself to searching for nearby substructures, both globular clusters and possible faint satellites.Current work is focused on the 16 closest Solo dwarfs, all within the virial radius (approximately 1 Mpc) of the Local Group. This subset has been characterized using consistent methods, despite their diversity in stellar mass and apparent size. The analysis highlights the extended stellar structure and morphology. We will examine trends with star formation history, and separation from a large host. This first subset emphasizes the survey’s unique challenges and advantages.The Solo Survey provides detailed look at the extended structure of dwarfs and characterizes the evolution of galaxies in the faint limit.

scholarly journals Constraints on Interactions and Mergers from dSph Galaxies and Globular Clusters

1999 ◽  
Vol 186 ◽  
pp. 52-52
Author(s):  
E.K. Grebel
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Local Group ◽  
Galactic Halo ◽  
Dwarf Galaxies ◽  
Thick Disk ◽  
History Of

Observations at high redshifts are revealing numerous interactions and ongoing mergers. Our own Milky Way is currently merging with the Sagittarius dwarf spheroidal (dSph) galaxy. Past mergers with dwarf galaxies may have contributed significantly to the Galactic halo and possibly to the thick disk. The properties of Local Group dSphs and halo globular clusters impose constraints on the merger history of the Milky Way.

scholarly journals Dwarf Galaxies as Cosmological Probes

2018 ◽  
Vol 14 (S344) ◽  
pp. 455-463
Author(s):  
Julio F. Navarro
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Dark Matter Halos ◽  
Too Big To Fail ◽  
Sharp Minimum ◽  
Luminous Galaxies ◽  
Small Scales ◽  
Low Mass

AbstractThe Lambda Cold Dark Matter (LCDM) paradigm makes specific predictions for the abundance, structure, substructure and clustering of dark matter halos, the sites of galaxy formation. These predictions can be directly tested, in the low-mass halo regime, by dark matter-dominated dwarf galaxies. A number of potential challenges to LCDM have been identified when confronting the expected properties of dwarfs with observation. I review our understanding of a few of these issues, including the “missing satellites” and the “too-big-to-fail” problems, and argue that neither poses an insurmountable challenge to LCDM. Solving these problems requires that most dwarf galaxies inhabit halos of similar mass, and that there is a relatively sharp minimum halo mass threshold to form luminous galaxies. These predictions are eminently falsifiable. In particular, LCDM predicts a large number of “dark” low-mass halos, some of which should have retained enough primordial gas to be detectable in deep 21 cm or Hα surveys. Detecting this predicted population of “mini-halos” would be a major discovery and a resounding success for LCDM on small scales.

scholarly journals Dwarf Galaxies: From the Epoch of Peak Star Formation to the Epoch of Reionization

2018 ◽  
Vol 14 (S344) ◽  
pp. 429-436
Author(s):  
Hakim Atek
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
High Redshift ◽  
Great Part ◽  
Star Formation History ◽  
Dark Matter Halos ◽  
Galaxy Surveys ◽  
Formation History ◽  
History Of ◽  
Low Mass

AbstractDwarf galaxies represent the dominant population at high redshift and they most likely contributed in great part to star formation history of the Universe and cosmic reionization. The importance of dwarf galaxies at high redshift has been mostly recognized in the last decade due to large progress in observing facilities allowing deep galaxy surveys to identify low-mass galaxies. This population appear to have extreme emission lines and ionizing properties that challenge stellar population models. Star formation follows a stochastic process in these galaxies, which has important implication on the ionizing photon production and its escape fraction whose measurements are challenging for both simulations and observations. Outstanding questions include: what are the physical properties at the origin of such extreme properties? What are the smallest dark matter halos that host star formation? Are dwarf galaxies responsible for cosmic reionization?

scholarly journals Hi and Galaxy Formation in Loose Groups

2004 ◽  
Vol 21 (4) ◽  
pp. 390-392
Author(s):  
Daniel J. Pisano
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Local Group ◽  
Dark Matter Halos ◽  
Early Results ◽  
Large Numbers ◽  
The Galaxy ◽  
Order Of Magnitude ◽  
Low Mass ◽  
High Velocity Clouds

AbstractModels of hierarchical galaxy formation predict that large numbers of low-mass, dark matter halos remain around galaxies today. These models predict an order of magnitude more halos than observed stellar satellites in the Local Group. One possible solution to this discrepancy is that the high-velocity clouds (HVCs) around the Milky Way may be associated with the excess dark matter halos and be the gaseous remnants of the galaxy formation process. If this is the case, then analogues to the HVCs should be visible in other groups. In this paper, I review the observations of Hi clouds lacking stars around other galaxies and in groups, present early results from our Hi survey of loose groups analogous to the Local Group, and discuss implications for the nature of HVCs and galaxy formation.

scholarly journals Probing the nature of dark matter with accreted globular cluster streams

2020 ◽  
Vol 501 (1) ◽  
pp. 179-200 ◽  
Author(s):  
Khyati Malhan ◽  
Monica Valluri ◽  
Katherine Freese
Keyword(s):  
Dark Matter ◽  
Globular Cluster ◽  
Particle Physics ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Density Profiles ◽  
Parallel Structures ◽  
Stellar Streams ◽  
Future Data ◽  
Low Mass

ABSTRACT The steepness of the central density profiles of dark matter (DM) in low-mass galaxy haloes (e.g. dwarf galaxies) is a powerful probe of the nature of DM. We propose a novel scheme to probe the inner profiles of galaxy subhaloes using stellar streams. We show that the present-day morphological and dynamical properties of accreted globular cluster (GC) streams – those produced from tidal stripping of GCs that initially evolved within satellite galaxies and later merged with the Milky Way (MW) – are sensitive to the central DM density profile and mass of their parent satellites. GCs that accrete within cuspy cold dark matter (CDM) subhaloes produce streams that are physically wider and dynamically hotter than streams that accrete inside cored subhaloes. A first comparison of MW streams ‘GD-1’ and ‘Jhelum’ (likely of accreted GC origin) with our simulations indicates a preference for cored subhaloes. If these results hold up in future data, the implication is that either the DM cusps were erased by baryonic feedback, or their subhaloes naturally possessed cored density profiles implying particle physics models beyond CDM. Moreover, accreted GC streams are highly structured and exhibit complex morphological features (e.g. parallel structures and ‘spurs’). This implies that the accretion scenario can naturally explain the recently observed peculiarities in some of the MW streams. We also propose a novel mechanism for forming ‘gaps’ in stellar streams when the remnant of the parent subhalo (which hosted the GC) later passes through the GC stream. This encounter can last a longer time (and have more of an impact) than the random encounters with DM subhaloes previously considered, because the GC stream and its parent subhalo are on similar orbits with small relative velocities. Current and future surveys of the MW halo will uncover numerous faint stellar streams and provide the data needed to substantiate our preliminary tests with this new probe of DM.

Hunting for Globular Clusters in the early universe

2019 ◽  
Vol 14 (S351) ◽  
pp. 212-215
Author(s):  
Frederika Phipps ◽  
Sadegh Khochfar ◽  
Anna Lisa Varri
Keyword(s):  
Dark Matter ◽  
High Resolution ◽  
Globular Clusters ◽  
Dwarf Galaxies ◽  
High Redshift ◽  
Stellar Systems ◽  
Mass Relation ◽  
Cosmological Context ◽  
Low Mass ◽  
Stellar Density

AbstractSetting the formation of globular clusters (GCs) within a cosmological context and characterising the properties of proto-GCs at high redshift is currently a major challenge. In this work, we address that challenge by exploring a suit of high-resolution cosmological simulations from the First Billion Years (FiBY) project z at ⩾6 to investigate theoretical scenarios concerning the formation of old, low-mass stellar systems with a particular focus on GCs. Two distinct groups of objects are identified in the simulations. The first group of objects, with a high baryon fraction, we associate with proto-GCs. The second group, that exhibit a high stellar fraction, could be forming ultra-faint dwarf galaxies (UFDs). The objects with high baryon fraction are promising proto-GC candidates because they have little to no dark matter (DM), have number densities consistent with predictions from the literature, are very compact and have a high stellar density. We fit and also assess the redshift-zero globular system mass - halo mass relation and find it provides a reasonable fit to our proto-GC objects, indicating that this relation is likely set at formation.

A New Reservoir of Dwarf Galaxy Candidates in the Centaurus A Group

2018 ◽  
Vol 14 (S344) ◽  
pp. 353-356
Author(s):  
Matthew A. Taylor ◽  
Paul Eigenthaler ◽  
Thomas H. Puzia ◽  
Roberto P. Muñoz ◽  
Karen X. Ribbeck ◽  
...  
Keyword(s):  
Local Group ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Elliptical Galaxy ◽  
Large Reservoir ◽  
Dwarf Spheroidal Galaxies ◽  
Low Mass ◽  
New Reservoir ◽  
Centaurus A

AbstractWe have searched optical u′g′r′i′z′ imaging of 22 deg2 centred on the nearby giant elliptical galaxy NGC 5128 for new dwarf galaxies in the Centaurus A group. We report 45 promising new candidates, which are broadly consistent with the properties of nearby dwarf spheroidal galaxies and extend the size-luminosity relation toward fainter total luminosities and smaller sizes for known dwarf galaxies outside the Local Group (LG). Altogether, these new results show NGC 5128 to be the host of a large reservoir of low-mass dwarf galaxies that is at least as rich as that of the LG and is ripe for detailed follow-up observations.

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