Gas accretion from halos to disks: observations, curiosities, and problems

AbstractAccretion of gas from the cosmic web to galaxy halos and ultimately their disks is a prediction of modern cosmological models but is rarely observed directly or at the full rate expected from star formation. Here we illustrate possible large-scale cosmic HI accretion onto the nearby dwarf starburst galaxy IC10, observed with the VLA and GBT. We also suggest that cosmic accretion is the origin of sharp metallicity drops in the starburst regions of other dwarf galaxies, as observed with the 10-m GTC. Finally, we question the importance of cosmic accretion in normal dwarf irregulars, for which a recent study of their far-outer regions sees no need for, or evidence of, continuing gas buildup.

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Substructure in Dwarf Galaxies

Publications of the Astronomical Society of Australia ◽

10.1071/as04040 ◽

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.

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Gas accretion from the cosmic web in the local Universe

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316010231 ◽

2014 ◽

Vol 11 (S308) ◽

pp. 390-393

Author(s):

J. Sánchez Almeida ◽

B. G. Elmegreen ◽

C. Muñoz-Tuñnón ◽

D. M. Elmegreen

Keyword(s):

Large Scale ◽

Dwarf Galaxies ◽

Local Universe ◽

Single Observation ◽

Star Forming ◽

Star Forming Regions ◽

Stellar Ages ◽

Gas Consumption ◽

Low Mass ◽

Gas Accretion

AbstractNumerical simulations predict that gas accretion from the cosmic web drives star formation in disks galaxies. The process is important in low mass haloes (< 1012M⊙), therefore, in the early universe when galaxies were low mass, but also in dwarf galaxies of the local universe. The gas that falls in is predicted to be tenuous, patchy, partly ionized, multi-temperature, and large-scale; therefore, hard to show in a single observation. One of the most compelling cases for gas accretion at work in the local universe comes from the extremely metal poor (XMP) galaxies. They show metallicity inhomogeneities associated with star-forming regions, so that large starbursts have lower metallicity than the underlying galaxy. Here we put forward the case for gas accretion from the web posed by XMP galaxies. Two other observational results are discussed too, namely, the fact that the gas consumption time-scale is shorter than most stellar ages, and the systematic morphological distortions of the HI around galaxies.

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Molecular Gas in the Centers of Barred and Starburst Galaxies

International Astronomical Union Colloquium ◽

10.1017/s0252921100019813 ◽

1994 ◽

Vol 140 ◽

pp. 282-292

Author(s):

Jeffrey D. P. Kenney

Keyword(s):

Star Formation ◽

Large Scale ◽

Starburst Galaxy ◽

Molecular Gas ◽

Barred Galaxies ◽

Twin Peaks ◽

Ngc 1068 ◽

Lindblad Resonance ◽

Inner Lindblad Resonance ◽

Co Emission

AbstractHigh resolution interferometric CO maps of the circumnuclear regions of several barred galaxies show intense CO emission arising from twin peaks, which are oriented perpendicular to the large-scale stellar bars and located where dust lanes intersect nuclear rings of HII regions. These twin gas concentrations can be explained by the crowding of gas streamlines near stellar inner Lindblad resonances. In the barred nuclear starburst galaxy NGC 3504, a large concentration of molecular gas is centered on the nucleus, apparently inside an inner Lindblad resonance. Star formation is consuming the gas most rapidly where the rotation curve is nearly solid body, suggesting that tidal shear helps control the rate of star formation. A comparison with M82 and NGC 1068 suggests that the starburst in NGC 3504 is in an early phase of its evolution, and that starburst evolution is strongly influenced by shear.

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H I Imaging Surveys: Gas and Galaxy Evolution in Different Environments

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311022435 ◽

2010 ◽

Vol 6 (S277) ◽

pp. 41-46

Author(s):

Jacqueline van Gorkom

Keyword(s):

Dark Matter ◽

Star Formation ◽

Galaxy Evolution ◽

Large Scale ◽

Large Scale Structure ◽

Local Universe ◽

Formation And Evolution ◽

Gas Accretion ◽

Optical Surveys ◽

Matter Component

AbstractOur understanding of the formation and evolution of galaxies and the large scale structure has advanced enormously over the last decade, thanks to an impressive synergy between theoretical and observational efforts. While the growth of the dark matter component seems well understood, the physics of the gas, during its accretion, removal and/or depletion is less well understood. Increasingly large scale optical surveys are tracing out the cosmic web of filaments and voids and mathematical tools have been developed to describe these structures and identify galaxies in specific environments. H I imaging surveys begin to answer the question: how do galaxies get and lose their gas. The best evidence for ongoing gas accretion is found in the lowest density environments, while removal of gas in the highest density environments stops star formation and reddens the galaxies. Although current H I emission surveys are limited to redshifts less than 0.2, this is where the LSS is best defined and much can be learned in the local universe.

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Low-redshift quasars in the SDSS Stripe 82 – II. Associated companion galaxies and signature of star formation

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3556 ◽

2020 ◽

Vol 501 (1) ◽

pp. 419-439

Author(s):

M B Stone ◽

D Bettoni ◽

R Falomo ◽

J K Kotilainen ◽

K Karhunen ◽

...

Keyword(s):

Star Formation ◽

Emission Line ◽

Large Scale ◽

Strong Influence ◽

Star Formation Rate ◽

Formation Rate ◽

Host Galaxy ◽

Starburst Galaxy ◽

Published Paper ◽

Larger Sample

ABSTRACT We present optical spectroscopy of the close companions of 22 low-redshift (z < 0.5) quasars (QSO) selected from a larger sample of QSO in the SDSS Stripe82 region for which both the host galaxy and the large-scale environments have been investigated in our previous work. The new observations extend the number of QSO studied in our previous paper on close companion galaxies of 12 quasars. Our analysis here covers all 34 quasars from both this work and the previously published paper. We find that half of them (15 QSO; ∼44 per cent) have at least one associated galaxy. Many (12 galaxies; ∼67 per cent) of the associated companions exhibit [O ii] 3727 Å emission line as signature of recent star formation. The star formation rate (SFR) of these galaxies is modest (median SFR ∼ 4.3 M⊙ yr−1). For eight QSO, we are also able to detect the starlight of the host galaxy from which three have a typical spectrum of a post-starburst galaxy. Our results suggest that quasars do not have a strong influence on the star formation of their companion galaxies.

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How do bound star clusters form?

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa659 ◽

2020 ◽

Vol 494 (1) ◽

pp. 624-641 ◽

Cited By ~ 9

Author(s):

Mark R Krumholz ◽

Christopher F McKee

Keyword(s):

Star Formation ◽

Large Scale ◽

Milky Way ◽

Star Formation Rate ◽

Formation Rate ◽

Free Fall ◽

Conveyor Belt ◽

Young Stellar Objects ◽

Gas Removal ◽

Gas Accretion

ABSTRACT Gravitationally bound clusters that survive gas removal represent an unusual mode of star formation in the Milky Way and similar spiral galaxies. While forming, they can be distinguished observationally from unbound star formation by their high densities, virialized velocity structures, and star formation histories that accelerate towards the present, but extend multiple free-fall times into the past. In this paper, we examine several proposed scenarios for how such structures might form and evolve, and carry out a Bayesian analysis to test these models against observed distributions of protostellar age, counts of young stellar objects relative to gas, and the overall star formation rate of the Milky Way. We show that models in which the acceleration of star formation is due either to a large-scale collapse or a time-dependent increase in star formation efficiency are unable to satisfy the combined set of observational constraints. In contrast, models in which clusters form in a ‘conveyor belt’ mode where gas accretion and star formation occur simultaneously, but the star formation rate per free-fall time is low, can match the observations.

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Star Formation History of Dwarf Galaxies in Cosmological Hydrodynamic Simulations

Advances in Astronomy ◽

10.1155/2010/651621 ◽

2010 ◽

Vol 2010 ◽

pp. 1-5 ◽

Cited By ~ 5

Author(s):

Kentaro Nagamine

Keyword(s):

Star Formation ◽

Large Scale ◽

Cold Dark Matter ◽

Dwarf Galaxies ◽

Star Formation History ◽

Hydrodynamic Simulations ◽

Cosmological Context ◽

Cold Dark Matter Model ◽

Formation History ◽

History Of

We examine the past and current work on the star formation (SF) histories of dwarf galaxies in cosmological hydrodynamic simulations. The results obtained from different numerical methods are still somewhat mixed, but the differences are understandable if we consider the numerical and resolution effects. It remains a challenge to simulate the episodic nature of SF history in dwarf galaxies at late times within the cosmological context of a cold dark matter model. More work is needed to solve the mysteries of SF history of dwarf galaxies employing large-scale hydrodynamic simulations on the next generation of supercomputers.

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Low Luminosity Galaxies

Publications of the Astronomical Society of Australia ◽

10.1071/as04046 ◽

2004 ◽

Vol 21 (4) ◽

pp. 360-365 ◽

Cited By ~ 4

Author(s):

J. I. Davies ◽

S. Sabatini ◽

S. Roberts

Keyword(s):

Star Formation ◽

Galaxy Formation ◽

Large Scale ◽

Dwarf Galaxies ◽

Dwarf Galaxy ◽

Building Blocks ◽

Large Mass ◽

Dark Matter Halos ◽

Cluster Environment ◽

Dense Cluster

AbstractLow luminosity (dwarf) galaxies play a crucial role in our current theories of galaxy and large scale structure formation. In the hierarchical picture they are the building blocks from which other structures form. These theories in their basic form overpredict the numbers of small dark matter halos (dwarf galaxies?) unless some form of star formation supression is invoked. In this paper we describe observations of dwarf galaxies in a range of different environments. We find that there are far too few dwarf galaxies in low density environments to be compatible with the theories. These observations are not consistent with an environment-independent mechanism suppressing dwarf galaxy formation. It is also not clear how these mechanisms can supress star formation if dwarf galaxies have large mass-to-light ratios (≈100). Either the whole idea of hierarchical galaxy formation has to be rejected or other environmentally dependent physical processes have to be invoked. We suggest that small, gas-rich dI galaxies have their evolution rapidly advanced as they move into the dense cluster environment.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318006816 ◽

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.

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