Intergalactic Matter and Radiation and its Bearing on Galaxy Formation and Evolution

Formation And Evolution ◽

The Universe ◽

Very High ◽

Theoretical Standpoint

An up-dated review is given of the evidence for the presence of intergalactic matter and radiation in the Universe. It is concluded that the only important constituents which may make a sizable contribution to the total mass-energy are intergalactic gas and condensed objects with a very high mass-to-light ratio. If the QSOs are not at cosmological distances, cold atomic hydrogen may still be the most important constituent and may contribute much more mass than do the galaxies. The X-ray observations still do not unambiguously show that very hot gas is present, though it is very likely on general grounds that some hot gas is present in clusters of galaxies.The question of whether or not large amounts of matter, enough to close the Universe, are present, remains unsettled. From the theoretical standpoint the answer depends almost completely on the approach taken to the problem of galaxy formation and to the cosmological model which is favoured.

New Results on DLA Systems: Statistics

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315010224 ◽

2015 ◽

Vol 11 (S319) ◽

pp. 40-40

Author(s):

Sandhya Rao ◽

David Turnshek ◽

Eric Monier ◽

Gendith Sardane

Keyword(s):

Galaxy Formation ◽

Mass Density ◽

Neutral Hydrogen ◽

Gas Content ◽

Neutral Gas ◽

Quasar Spectra ◽

Formation And Evolution ◽

Space Data ◽

AbstractThe damped Lyman-α absorption-line systems (DLAs) that are observed in quasar spectra arise in neutral-gas-rich regions of intervening galaxies. With the highest neutral hydrogen column densities observed (N(HI) ⩾ 2 × 1020 atoms cm−2), they are known to trace the bulk of the neutral gas content of the Universe, and are thus powerful probes of galaxy formation and evolution. However, DLAs are extremely rare, and since the Lyman-α line falls in the UV for redshifts z < 1.65, not many are known at low redshift due to the limited availability of space data. Our HST surveys for DLAs in strong MgII absorbers have been successful at showing that MgII can be used as an unbiased tracer of DLAs. We present new results on their incidence, or redshift number density, dn/dz, and cosmological neutral gas mass density, ΩDLA, at redshifts 0.11 ⩽ z ⩽ 1.65, and incorporate results from higher and lower redshift studies in the literature to derive the evolution of neutral gas in the Universe.

THE LINK BETWEEN GALAXIES AND DARK MATTER

International Journal of Modern Physics D ◽

10.1142/s0218271811019840 ◽

2011 ◽

Vol 20 (10) ◽

pp. 1771-1777

Author(s):

HOUJUN MO

Keyword(s):

Dark Matter ◽

Galaxy Formation ◽

Luminosity Function ◽

The Other ◽

Dark Matter Halos ◽

The Galaxy ◽

Galaxy Halo ◽

Formation And Evolution ◽

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.

Disk Galaxies in the Magneticum Pathfinder Simulations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314009491 ◽

2014 ◽

Vol 10 (S309) ◽

pp. 145-148 ◽

Cited By ~ 3

Author(s):

Rhea-Silvia Remus ◽

Klaus Dolag ◽

Lisa K. Bachmann ◽

Alexander M. Beck ◽

Andreas Burkert ◽

...

Keyword(s):

Galaxy Formation ◽

Mass Function ◽

Disk Galaxies ◽

Physical Processes ◽

Mass Size ◽

Formation And Evolution ◽

Galaxy Populations ◽

Size Relation ◽

AbstractWe presentMagneticum Pathfinder, a new set of hydrodynamical cosmological simulations covering a large range of cosmological scales. Among the important physical processes included in the simulations are the chemical and thermodynamical evolution of the diffuse gas as well as the evolution of stars and black holes and the corresponding feedback channels. In the high resolution boxes aimed at studies of galaxy formation and evolution, populations of both disk and spheroidal galaxies are self-consistently reproduced. These galaxy populations match the observed stellar mass function and show the same trends for disks and spheroids in the mass–size relation as observations from the SDSS. Additionally, we demonstrate that the simulated galaxies successfully reproduce the observed specific angular-momentum–mass relations for the two different morphological types of galaxies. In summary, theMagneticum Pathfindersimulations are a valuable tool for studying the assembly of cosmic and galactic structures in the universe.

The Cosmic Chemical Evolution as seen by the Brightest Events in the Universe

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310000426 ◽

2009 ◽

Vol 5 (S265) ◽

pp. 139-146 ◽

Author(s):

Sandra Savaglio

Keyword(s):

Chemical Evolution ◽

Galaxy Formation ◽

Gamma Ray ◽

Host Galaxies ◽

First Stars ◽

Galaxy Surveys ◽

Formation And Evolution ◽

Field Galaxy ◽

AbstractGamma-ray bursts (GRBs) are the brightest events in the universe. They have been used in the last five years to study the cosmic chemical evolution, from the local universe to the first stars. The sample size is still relatively small when compared to field galaxy surveys. However, GRBs show a universe that is surprising. At z > 2, the cold interstellar medium in galaxies is chemically evolved, with a mean metallicity of about 1/10 solar. At lower redshift (z < 1), metallicities of the ionized gas are relatively low, on average 1/6 solar. Not only is there no evidence of redshift evolution in the interval 0 < z < 6.3, but also the dispersion in the ~30 objects is large. This suggests that the metallicity of host galaxies is not the physical quantity triggering GRB events. From the investigation of other galaxy parameters, it emerges that active star-formation might be a stronger requirement to produce a GRB. Several recent striking results strongly support the idea that GRB studies open a new view on our understanding of galaxy formation and evolution, back to the very primordial universe at z ~ 8.

Cooling Flows and the Formation of Dark matter

Symposium - International Astronomical Union ◽

10.1017/s0074180900150181 ◽

1987 ◽

Vol 117 ◽

pp. 201-213 ◽

Author(s):

A. C. Fabian ◽

K. A. Arnaud ◽

P. A. Thomas

Keyword(s):

Dark Matter ◽

Galaxy Formation ◽

Elliptical Galaxies ◽

High Mass ◽

Clusters Of Galaxies ◽

Local Models ◽

X Ray ◽

Cooling Flows ◽

Mass Profiles

The distribution of matter condensing out of cooling flows in clusters of galaxies and individual elliptical galaxies has been studied using X-ray data and is found to resemble the expected mass profiles of the underlying galaxies. Most of the cooled gas must create objects of high mass-to-light ratio, although some more normal stars are produced. Cooling flows provide an observable mechanism for the continual formation of dark matter around galaxies. Since the conditions at galaxy formation are similar to those in cooling flows if the gas reaches the virial temperature, we suggest that they are local models of galaxy formation.

Feedback from AGN: The Kinetic/Radio Luminosity Function

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310006861 ◽

2009 ◽

Vol 5 (S267) ◽

pp. 402-402

Author(s):

Gabriele Melini ◽

Fabio La Franca ◽

Fabrizio Fiore

Keyword(s):

Galaxy Formation ◽

Probability Distribution Function ◽

Luminosity Function ◽

Complete Sample ◽

X Ray ◽

Formation And Evolution ◽

Radio Luminosity Function ◽

Radio Power ◽

Good Agreement

We have measured the probability distribution function of the ratio RX = log L1.4/LX, where L1.4/LX = ν Lν(1.4 GHz)/LX(2–10 keV), between the 1.4 GHz and the unabsorbed 2–10 keV luminosities and its dependence on LX and z. We have used a complete sample of ~1800 hard X-ray selected AGN, observed in the 1.4 GHz band, cross-correlated in order to exclude FR II-type objects, and thus obtain a contemporaneous measure of the radio and X-ray emission. The distribution P(RX|LX,z) is shown in Figure 1. Convolution of the distribution P(RX|LX,z) with the 2–10 keV X-ray AGN luminosity function from La Franca et al. (2005) and the relations between radio power and kinetic energy from Best et al. (2006) and Willott et al. (1999) allows us to derive the AGN kinetic power and its evolution. As shown in Figure 1, our results are in good agreement with the predictions of the most recent models of galaxy formation and evolution (e.g., Croton et al. 2006), where AGN radio feedback is required to quench the star formation.

Supernovae and the Galactic Ecosystem

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313009587 ◽

2013 ◽

Vol 9 (S296) ◽

pp. 273-281 ◽

Author(s):

Q. Daniel Wang

Keyword(s):

Galaxy Formation ◽

Supernova Remnants ◽

Theoretical Work ◽

Low Density ◽

Feedback Process ◽

Hot Gas ◽

Stellar Feedback ◽

Formation And Evolution ◽

The Impact

AbstractSupernovae are the dominant source of stellar feedback, which plays an important role in regulating galaxy formation and evolution. While this feedback process is still quite uncertain, it is probably not due to individual supernova remnants as commonly observed. Most supernovae likely take place in low-density, hot gaseous environments, such as superbubbles and galactic bulges, and typically produce no long-lasting bright remnants. I review recent observational and theoretical work on the impact of such supernovae on galaxy ecosystems, particularly on hot gas in superbubbles and galactic spheroids.

Re-ionization of the IGM — Massive Stars versus QSOs

Symposium - International Astronomical Union ◽

10.1017/s0074180900213089 ◽

2003 ◽

Vol 212 ◽

pp. 687-695 ◽

Author(s):

Piero Madau

Keyword(s):

Galaxy Formation ◽

Cold Dark Matter ◽

Mechanical Energy ◽

Density Fluctuations ◽

Atomic Processes ◽

Feedback Mechanisms ◽

History Of ◽

Formation And Evolution ◽

In popular cold dark matter cosmological scenarios, stars may have first appeared in significant numbers around a redshift of 10 or so, as the gas within protogalactic halos with virial temperatures Tvir ≃ 20 000 K (corresponding to masses comparable to those of present-day dwarf ellipticals) cooled rapidly due to atomic processes and fragmented. It is this ‘second generation’ of subgalactic stellar systems, aided perhaps by an early population of accreting black holes in their nuclei, which may have generated the ultraviolet radiation and mechanical energy that ended the cosmic ‘dark ages’ and reheated and re-ionized most of the hydrogen in the universe by a redshift of z = 6. The detailed history of the universe during, and soon after these crucial formative stages, depends on the power-spectrum of density fluctuations on small scales and on a complex network of poorly understood feedback mechanisms, and is one of the missing links in galaxy formation and evolution studies.

Dust in Evolving Galaxies

Highlights of Astronomy ◽

10.1017/s1539299600014088 ◽

2002 ◽

Vol 12 ◽

pp. 460-463 ◽

Author(s):

Paola Andreani

Keyword(s):

Galaxy Formation ◽

Dust Emission ◽

Stellar Activity ◽

History Of ◽

Crucial Information ◽

Entire History ◽

Formation And Evolution ◽

Lower Luminosity ◽

AbstractI will first review the observational evidence relating dust emission and the energy production in the far-IR/submm range. This latter contains crucial information on the global baryons transformation and the related stellar activity in the Universe. Present knowledge on this topic relies mainly on the far-IR local surveys of IRAS and ISO missions and on submm/mm surveys performed with SCUBA and MAMBO arrays. Further constraints are provided by the measurements of the Cosmic far-IR Background (CFIRB). Our scanty knowledge of galaxy formation and evolution is mainly caused by the difficulties of unveiling stellar activity at redshifts larger than 1 and at present we may only have detected massive objects in a transient hyper-luminous phase. We still lack an unbiased census of the much more numerous population of lower luminosity dusty objects. It will soon be possible to disclose the entire history of evolving dusty objects, and therefore of the stellar activity, selecting unbiased samples out of far-IR imaging and photometry in deep far-IR surveys.

AGN feedback and galaxy evolution in nearby galaxy groups using CLoGS

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320001507 ◽

2019 ◽

Vol 15 (S359) ◽

pp. 180-181

Author(s):

Konstantinos Kolokythas ◽

Keyword(s):

Galaxy Evolution ◽

Galaxy Formation ◽

Gas Content ◽

Molecular Gas ◽

Nearby Galaxy ◽

Complete Sample ◽

X Ray ◽

Galaxy Groups ◽

Formation And Evolution

AbstractMuch of the evolution of galaxies takes place in groups where feedback has the greatest impact on galaxy formation and evolution. We summarize results from studies of the central brightest group early-type galaxies (BGEs) of an optically selected, statistically complete sample of 53 nearby groups (<80 Mpc; CLoGS sample), observed in radio 235/610 MHz (GMRT), CO (IRAM/APEX) and X-ray (Chandra and XMM-Newton) frequencies. We characterize the radio-AGN population of the BGEs, their group X-ray environment and examine the jet energetics impact on the intra-group gas. We discuss the relation between the radio properties of the BGEs and their group X-ray environment along with the relation between the molecular gas content and the star formation that BGEs present. We conclude that AGN feedback in groups can appear as relatively gentle near-continuous thermal regulation, but also as extreme AGN activity which could potentially shut down cooling for longer periods.