scholarly journals Starbursts and Extra-planar Hα from SINGG

2004 ◽  
Vol 217 ◽  
pp. 287-293 ◽  
Author(s):  
Gerhardt R. Meurer
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Neutral Hydrogen ◽  
Neutral Gas ◽  
Galactic Winds ◽  
First Pass ◽  
Show Evidence ◽  
Galactic Sources ◽  
Hydrogen Mass ◽  
Larger Sample

The NOAO Survey for Ionization in Neutral Gas Galaxies (SINGG) is the largest star formation survey of an H I selected sample. Since the selection is made without regard to optical morphology, it is not biased toward or against “interesting” types of galaxies; thus SINGG is an ideal sample for studying galaxy demographics. Of a sample of 90 extra-galactic sources observed in photometric conditions, all are detected in Hα. This indicates that dormant galaxies, those containing an appreciable ISM but no star formation, are at best rare. We have made first pass morphological surveys for starbursts, as judged by Hα surface brightness, and outflows as judged by extra-planar Hα. We find that about 15% of the sources contain starbursts, with little dependence on the neutral hydrogen mass MHI. Nearly one half of a sample ~ 35 edge-on galaxies show evidence for extra-planar Hα having a scale size of 0.5 Kpc or larger, while nearly one quarter have extra-planar Hα features 1.0 Kpc in size or larger. There is a hint that high MHI systems preferentially have displaced outflows (chimneys, or fountains) while central outflows (galactic winds) preferentially occur in low MHI systems. However, a larger sample (e.g. the full SINGG survey) is needed to confirm this trend.

scholarly journals Damped Lyman-α Absorbers in Cosmological SPH Simulations: the “Metallicity Problem”

2005 ◽  
Vol 216 ◽  
pp. 266-273
Author(s):  
Kentaro Nagamine ◽  
Volker Springel ◽  
Lars Hernquist
Keyword(s):  
Star Formation ◽  
Cold Dark Matter ◽  
Mass Density ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Galactic Winds ◽  
Particle Hydrodynamics ◽  
Order Of Magnitude ◽  
Smoothed Particle ◽  
Hydrogen Mass

We study the distribution of star formation rate (SFR) and metallicity of damped Lyman-α absorbers (DLAs) using cosmological smoothed particle hydrodynamics (SPH) simulations of the Λ cold dark matter (CDM) model. Our simulations include a phenomenological model for feedback by galactic winds which allows us to examine the effect of galactic outflows on the distribution of SFR and metallicity of DLAs. For models with strong galactic winds, we obtain good agreement with recent observations with respect to total neutral hydrogen mass density, NHI column-density distribution, abundance of DLAs, and for the distribution of SFR in DLAs. However, we also find that the median metallicity of simulated DLAs is higher than the values typically observed by nearly an order of magnitude. This discrepancy with observations could be due to shortcomings in the treatment of the supernova feedback or the multiphase structure of the gas in our current simulations. Recent observations by Wolfe et al. (2003a,b) seem to point to the same problem; i.e. the observed DLA metallicities are much lower than those expected from the (either observed or simulated) DLA star formation rates, a puzzle that has been known as the “missing metals”-problem for the globally averaged quantities.

The Hi Neighborhoods Around STARBIRDS

2018 ◽  
Vol 14 (S344) ◽  
pp. 280-282
Author(s):  
Megan C. Johnson ◽  
Kristen B. W. McQuinn ◽  
John Cannon ◽  
Charlotte Martinkus ◽  
Evan Skillman ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
Neutral Hydrogen ◽  
Tidal Interactions ◽  
Low Surface Brightness ◽  
The Galaxy ◽  
Green Bank Telescope ◽  
Intense Star Formation

AbstractStarbursts are finite periods of intense star formation (SF) that can dramatically impact the evolutionary state of a galaxy. Recent results suggest that starbursts in dwarf galaxies last longer and are distributed over more of the galaxy than previously thought, with star formation efficiencies (SFEs) comparable to spiral galaxies, much higher than those typical of non-bursting dwarfs. This difference might be explainable if the starburst mode is externally triggered by gravitational interactions with other nearby systems. We present new, sensitive neutral hydrogen observations of 18 starburst dwarf galaxies, which are part of the STARburst IRregular Dwarf Survey (STARBIRDS) and each were mapped with the Green Bank Telescope (GBT) and/or Parkes Telescope in order to study the low surface brightness gas distributions, a common tracer for tidal interactions.

scholarly journals The Neutral Hydrogen Cosmological Mass Density at z = 5

2016 ◽  
Vol 11 (S321) ◽  
pp. 309-314
Author(s):  
Neil H. M. Crighton ◽  
Michael T. Murphy ◽  
J. Xavier Prochaska ◽  
Gábor Worseck ◽  
Marc Rafelski ◽  
...  
Keyword(s):  
Star Formation ◽  
Functional Form ◽  
Mass Density ◽  
High Redshift ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Ionized Gas ◽  
Galactic Winds ◽  
Lower Column ◽  
Systematic Effects

AbstractWe present the largest homogeneous survey of redshift > 4.4 damped Lyα systems (DLAs) using the spectra of 163 quasars that comprise the Giant Gemini GMOS (GGG) survey. With this survey we make the most precise high-redshift measurement of the cosmological mass density of neutral hydrogen, ΩHI. After correcting for systematic effects using a combination of mock and higher-resolution spectra, we find ΩHI= 0.98+0.20-0.18 × 10−3 at 〈z〉 = 4.9, assuming a 20% contribution from lower column density systems below the DLA threshold. By comparing to literature measurements at lower redshifts, we show that ΩHI can be described by the functional form ΩHI(z) ∝ (1 + z)0.4. This gradual decrease from z = 5 to 0 suggests that in the galaxies which dominate the cosmic star formation rate, Hi is a transitory gas phase fuelling star formation which must be continually replenished by more highly-ionized gas from the intergalactic medium, and from recycled galactic winds.

scholarly journals Star Formation in Damped Lyman α Selected Galaxies

2007 ◽  
Vol 3 (S244) ◽  
pp. 284-288
Author(s):  
Lise Christensen
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
Disk Galaxies ◽  
Local Universe ◽  
High Redshift Galaxies ◽  
Neutral Gas ◽  
Integral Field Spectroscopy ◽  
Integral Field

AbstractI present results from an ongoing survey to study galaxies associated with damped Lyman-α (DLA) systems at redshifts z>2. Integral field spectroscopy is used to search for Lyα emission line objects at the wavelengths where the emission from the quasars have been absorbed by the DLAs. The DLA galaxy candidates detected in this survey are found at distances of 10–20 kpc from the quasar line of sight, implying that galaxies are surrounded by neutral hydrogen at large distances. If we assume that the distribution of neutral gas is exponential, the scale length of the neutral gas is ~6 kpc, similar to large disk galaxies in the local Universe. The emission line luminosities imply smaller star formation rates compared to other high redshift galaxies found in luminosity selected samples.

scholarly journals Evolution of the cold gas fraction and the star formation history: Prospects with current and future radio facilities

2018 ◽  
Vol 35 ◽  
Author(s):  
S. J. Curran
Keyword(s):  
Star Formation ◽  
Neutral Hydrogen ◽  
Star Formation History ◽  
Spin Temperature ◽  
Star Forming ◽  
Neutral Gas ◽  
Contemporary Sample ◽  
Formation History ◽  
Radio Band ◽  
Cold Gas

AbstractIt has recently been shown that the abundance of cold neutral gas may follow a similar evolution as the star formation history. This is physically motivated, since stars form out of this component of the neutral gas and if the case, would resolve the long-standing issue that there is a clear disparity between the total abundance of neutral gas and star-forming activity over the history of the Universe. Radio-band 21-cm absorption traces the cold gas and comparison with the Lyman-α absorption, which traces all of the gas, provides a measure of the cold gas fraction, or the spin temperature, Tspin. The recent study has shown that the spin temperature (degenerate with the ratio of the absorber/emitter extent) appears to be anti-correlated with the star formation density, ψ*, with 1/Tspin undergoing a similar steep evolution as ψ* over redshifts of 0 ≲ z ≲ 3, whereas the total neutral hydrogen exhibits little evolution. Above z ∼ 3, where ψ* shows a steep decline with redshift, there are insufficient 21-cm data to determine whether 1/Tspin continues to follow ψ*. Knowing this is paramount in ascertaining whether the cold neutral gas does trace the star formation over the Universe’s history. We explore the feasibility of resolving this with 21-cm observations of the largest contemporary sample of reliable damped Lyman-α absorption systems and conclude that, while today’s largest radio interferometers can reach the required sensitivity at z ≲ 3.5, the Square Kilometre Array is required to probe higher redshifts.

scholarly journals Galactic Winds in Low-Mass Galaxies

2018 ◽  
Vol 14 (S344) ◽  
pp. 301-304
Author(s):  
Kristen B. W. McQuinn ◽  
Liese van Zee ◽  
Evan D. Skillman
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Critical Role ◽  
Ionized Gas ◽  
Stellar Feedback ◽  
Galactic Winds ◽  
Low Surface Brightness ◽  
The Galaxy ◽  
Show Evidence ◽  
Low Mass

AbstractMass-loss via stellar-feedback driven outflows is predicted to play a critical role in the baryon cycle of low-mass galaxies. However, observational constraints on warm winds are limited as outflows are transient, intrinsically low-surface brightness events and, thus, difficult to detect. Here, we search for outflows in a sample of eleven nearby starburst dwarf galaxies which are strong candidates for outflows. Despite deep H? imaging on galaxies, only a fraction of the sample show evidence of winds. The spatial extent of all detected ionized gas is limited and would still be considered part of the ISM by simulations. These new observations indicate that the physical extent of warm phase outflows is modest and most of the mass will be recycled to the galaxy. The sample is part of the panchromatic STARBurst IRegular Dwarf Survey (STARBIRDS) designed to characterize the starburst phenomenon and its impact on the evolution of low-mass galaxies.

scholarly journals DLAs AND GALAXY FORMATION

2007 ◽  
Vol 22 (32) ◽  
pp. 2413-2427
Author(s):  
KENTARO NAGAMINE
Keyword(s):  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Mass Density ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
Infrared Telescope ◽  
Neutral Gas ◽  
Galactic Winds ◽  
Cold Dark Matter Model ◽  
The Future

Damped Lyman-α systems (DLAs) are useful probes of star formation and galaxy formation at high-redshift (hereafter high-z). We study the physical properties of DLAs and their relationship to Lyman break galaxies (LBGs) using cosmological hydrodynamic simulations based on the concordance Λ cold dark matter model. Fundamental statistics such as global neutral hydrogen (H I) mass density, H I column density distribution function, DLA rate-of-incidence and mean halo mass of DLAs are reproduced reasonably well by the simulations, but with some deviations that need to be understood better in the future. We discuss the feedback effects by supernovae and galactic winds on the DLA distribution. We also compute the [C II] emission from neutral gas in high-z galaxies, and make predictions for the future observations by the Atacama Large Millimeter Array (ALMA) and Space Infrared Telescope for Cosmology and Astrophysics (SPICA). Agreement and disagreement between simulations and observations are discussed, as well as the future directions of our DLA research.

scholarly journals A Review of Recent Observations of Galactic Winds Driven by Star Formation

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 138 ◽  
Author(s):  
David Rupke
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Near Infrared ◽  
Current Model ◽  
Imaging Spectroscopy ◽  
Star Forming ◽  
Neutral Gas ◽  
Direct Observations ◽  
Galactic Winds ◽  
Large Numbers

Galaxy-scale outflows of gas, or galactic winds (GWs), driven by energy from star formation are a pivotal mechanism for regulation of star formation in the current model of galaxy evolution. Observations of this phenomenon have proliferated through the wide application of old techniques on large samples of galaxies, the development of new methods, and advances in telescopes and instrumentation. I review the diverse portfolio of direct observations of stellar GWs since 2010. Maturing measurements of the ionized and neutral gas properties of nearby winds have been joined by exciting new probes of molecular gas and dust. Low-z techniques have been newly applied in large numbers at high z. The explosion of optical and near-infrared 3D imaging spectroscopy has revealed the complex, multiphase structure of nearby GWs. These observations point to stellar GWs being a common feature of rapidly star-forming galaxies throughout at least the second half of cosmic history, and suggest that scaling relationships between outflow and galaxy properties persist over this period. The simple model of a modest-velocity, biconical flow of multiphase gas and dust perpendicular to galaxy disks continues to be a robust descriptor of these flows.

Variation of the amount of hydrogen along the galactic ridge

1967 ◽  
Vol 31 ◽  
pp. 171-172
Author(s):  
Th. Schmidt-Kaler
Keyword(s):  
Surface Brightness ◽  
Milky Way ◽  
Neutral Hydrogen ◽  
Line Of Sight ◽  
Optical Surface ◽  
Hydrogen Density ◽  
Continuous Radiation ◽  
Galactic Longitude

The integralNHof neutral-hydrogen density along the line of sight is determined from the Kootwijk and Sydney surveys. The run ofNHwith galactic longitude agrees well with that of thermal continuous radiation and that of the optical surface brightness of the Milky Way.

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