scholarly journals Exploring the Environment of the most powerful Explosions

2015 ◽  
Vol 11 (A29B) ◽  
pp. 261-262
Author(s):  
Antonino Cucchiara ◽  
Mark Rafelski ◽  
Michele Fumagalli ◽  
Daniel Kocevski ◽  
Jason X. Prochaska ◽  
...  
Keyword(s):  
Star Formation ◽  
Absorption Spectroscopy ◽  
Star Formation Rate ◽  
Massive Stars ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Enriched Environment ◽  
Intense Star Formation ◽  
Cold Gas

AbstractMore than 60 GRBs at z ≳ 1.5 reside in the vicinity of dense, cold gas as probed by the measured neutral hydrogen via afterglow absorption spectroscopy. We present the largest sample of GRB-DLAs to date in comparison with a sample of DLAs along quasars: the metallicity of the GRB hosts represents a unique tool to understand if this particular subset of galaxies can be the key ingredient for GRB formation (and massive stars) at any redshift as well as the overall cosmic star-formation rate. We show that GRB-DLAs live in a metal enriched environment, especially at z ≳ 4, likely the result of recent intense star formation and/or SNe episodes. We also derive that our metallicity measurements are broadly consistent with a mild metallicity bias for the GRB formation.

scholarly journals xGASS: cold gas content and quenching in galaxies below the star-forming main sequence

2020 ◽  
Vol 493 (2) ◽  
pp. 1982-1995 ◽  
Author(s):  
Steven Janowiecki ◽  
Barbara Catinella ◽  
Luca Cortese ◽  
Amelie Saintonge ◽  
Jing Wang
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Gas Content ◽  
Gas Reservoirs ◽  
Star Forming ◽  
Correct Model ◽  
Gas Measurements ◽  
Cold Gas

ABSTRACT We use H i and H2 global gas measurements of galaxies from xGASS and xCOLD GASS to investigate quenching paths of galaxies below the Star forming main sequence (SFMS). We show that the population of galaxies below the SFMS is not a 1:1 match with the population of galaxies below the H i and H2 gas fraction scaling relations. Some galaxies in the transition zone (TZ) 1σ below the SFMS can be as H i-rich as those in the SFMS, and have on average longer gas depletion time-scales. We find evidence for environmental quenching of satellites, but central galaxies in the TZ defy simple quenching pathways. Some of these so-called ‘quenched’ galaxies may still have significant gas reservoirs and be unlikely to deplete them any time soon. As such, a correct model of galaxy quenching cannot be inferred with star formation rate (or other optical observables) alone, but must include observations of the cold gas. We also find that internal structure (particularly, the spatial distribution of old and young stellar populations) plays a significant role in regulating the star formation of gas-rich isolated TZ galaxies, suggesting the importance of bulges in their evolution.

scholarly journals Recent star formation in the Hi dominated outer regions of early-type galaxies

2016 ◽  
Vol 11 (S321) ◽  
pp. 279-279
Author(s):  
Mustafa K. Yıldız ◽  
Paolo Serra ◽  
Reynier F. Peletier ◽  
Tom A. Oosterloo ◽  
Pierre-Alain Duc
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Radial Profile ◽  
Control Sample ◽  
Neutral Hydrogen ◽  
Stellar Mass ◽  
Early Type ◽  
Stellar Kinematics ◽  
The Impact

AbstractContextAccording to the ATLAS3D project, about 20 percent of all nearby early-type galaxies (D < 42 Mpc; MK < -21.5 mag; stellar mass Mstars ≳ 6 × 109 M⊙) outside clusters are surrounded by a disc or ring of low-column-density neutral hydrogen (Hi) gas with typical radii of tens of kpc, much larger than the stellar body.AimsOur aim is to understand the impact of these gas systems on the host galaxies, in particular, whether there is any recent star formation related to the Hi and effect of recent star formation on the host early-type galaxies.Methods and sampleWe analyse the distribution of star formation out to large radii by using resolved Hi images together with UV and optical images. We calculate the UV-UV and UV-optical colours in two apertures, 1-3 and 3-10 Reff. Using FUV emission as a proxy for star formation, we also estimate the integrated star formation rate in the outer regions. Our sample consists of 18 Hi-rich galaxies as well as 55 control galaxies where no Hi has been detected. We select the control sample galaxies to match the Hi-rich galaxies in stellar mass, environment, distance and stellar kinematics.ResultsIn half of the Hi-rich galaxies the radial UV profile changes slope at the position of the Hi radial profile peak. We find that the FUV-NUV and UV-optical colours in the first and second apertures of the Hi-rich galaxies are on average 0.5 and 0.8 mag bluer than the Hi-poor ones, respectively. We also find that the Hi-rich early-type galaxies have colour gradients that are almost 2 times stronger than the Hi-poor ones. we estimate the integrated star formation rate in the outer regions (R > 1 Reff) to be on average ~ 6.1×10−3 M⊙ yr−1 for the Hi-rich galaxies. We find that the gas depletion time in the outermost region (3-10 Reff) is ~ 80 Gyrs, which is similar to that estimated for the outskirts of spirals.ConclusionsStudying the stellar populations in early type galaxies with and without Hi, we find that galaxies with Hi generally show UV and UV-Optical colours in the outer parts that are bluer than those of early-type galaxies without Hi. This shows that the Hi is actively involved in recent star formation. The star formation rate in the outer regions is too low to build a stellar disc, and therefore change the morphology of the host even when integrated over several Gyrs. Star formation in outermost regions does not depend on the type of the galaxies.

scholarly journals Connection between the Star Formation Rate and the Gamma-Ray Bursts

2012 ◽  
Vol 8 (S292) ◽  
pp. 334-334
Author(s):  
Attila Mészáros ◽  
Zsolt Bagoly ◽  
Lajos G. Balázs ◽  
István Horváth
Keyword(s):  
Star Formation ◽  
Gamma Ray ◽  
Star Formation Rate ◽  
Massive Stars ◽  
Formation Rate ◽  
Gamma Ray Bursts

AbstractIt is remarkable that the long gamma-ray bursts, as objects connected with the supernovae - i.e. with the end of the massive stars, trace the star formation rate. This connection is discussed in this contribution. The presentation is in essence a recapitulation of the article Mészáros A. et al. A&A, 2006, 455, 785.

scholarly journals Are LGRBs biased tracers of star formation? Clues from the host galaxies of the Swift/BAT6 complete sample of LGRBs

2015 ◽  
Vol 11 (A29B) ◽  
pp. 249-250
Author(s):  
Susanna D. Vergani ◽  
Keyword(s):  
Star Formation ◽  
Gamma Ray ◽  
Star Formation Rate ◽  
Massive Stars ◽  
Formation Rate ◽  
Gamma Ray Bursts ◽  
Host Galaxies ◽  
Complete Sample ◽  
Rate Versus ◽  
High Metallicity

AbstractLong gamma-ray bursts (LGRBs) are associated to the deaths of massive stars and could thus be used as a potentially powerful tool to trace cosmic star formation. However the conditions needed to produce a LGRBs may introduce a bias in the LGRB rate versus star formation rate (SFR) relation (called LGRB efficiency hereafter).We have undertaken a study of the properties of the host galaxies of the BAT6 complete sample of LGRB to improve our knowledge on the LGRB efficiency, its redshift evolution, and the factor affecting it. This is the base to properly use LGRBs as SFR tracers.We show that at z < 1 LGRBs are not direct SFR tracers because they tend to avoid high-metallicity galaxies. The use of the BAT6 complete sample keeps this result from being affected by possible biases that could have influenced past results based on incomplete samples. The preference for low (but not extremely low) metallicities can be a consequence of the particular conditions needed for the progenitor star to produce a GRB.

scholarly journals Massive stars in low-redshift galaxies

2003 ◽  
Vol 212 ◽  
pp. 663-670
Author(s):  
Marie-A. Treyer
Keyword(s):  
Star Formation ◽  
Unit Volume ◽  
Star Formation Rate ◽  
Massive Stars ◽  
Formation Rate ◽  
Empirical Models ◽  
Star Formation History ◽  
Local Universe ◽  
Formation History ◽  
Multi Wavelength

I summarize the method commonly used to estimate the current star formation rate per unit volume as a function of redshift from various star formation diagnostics, as well as the often conflicting results from the various multi-wavelength datasets collected in recent years. Combined together, and with the help of theoretical and empirical models, these results allow us to address the issues of excitation, reddening, metallicity, and star formation history in individual galaxies at low redshift. They seem to point to the fact, that a lot of the star formation in the local universe, and potentially at all redshift, occurs in burst mode rather than continuously.

scholarly journals The Red MSX Source Survey - Massive Star Formation in the Milky Way

2009 ◽  
Vol 5 (H15) ◽  
pp. 801-801
Author(s):  
Stuart Lumsden ◽  
Melvin Hoare ◽  
Ben Davis ◽  
Keyword(s):  
Star Formation ◽  
Accretion Disks ◽  
Massive Star ◽  
Milky Way ◽  
Star Formation Rate ◽  
Massive Stars ◽  
Formation Rate ◽  
Massive Star Formation

AbstractWe present the results of a Galaxy-wide survey for young massive stars still in the process of formation. Our data are consistent with a model in which the stars form through accretion disks with the overall Galactic star formation rate being 3 M⊙ per year.

scholarly journals The star formation rate in the inner Milky Way Galaxy

2012 ◽  
Vol 8 (S292) ◽  
pp. 98-98
Author(s):  
Oscar Cavichia ◽  
Mercedes Mollá ◽  
Roberto D. D. Costa ◽  
Walter J. Maciel
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Star Formation Rate ◽  
Massive Stars ◽  
Galactic Disk ◽  
Formation Rate ◽  
Specific Pattern ◽  
Gas Flows ◽  
Milky Way Galaxy ◽  
Stellar Formation

AbstractThe present star formation rate (SFR) in the inner Galaxy is puzzling for the chemical evolution models (CEM). No static CEM is able to reproduce the peak of the SFR in the 4 kpc ring. The main reason is probably a shortage of gas, which could be due to the dynamical effects produced by the galactic bar, not considered by these models. We developed a CEM that includes radial gas flows in order to mimic the effects of the galactic bar in the first 5 kpc of the galactic disk. In this model, the star formation (SF) is a two-step process: first, the diffuse gas forms molecular clouds. Then, stars form from cloud-cloud collisions or by the interaction between massive stars and the molecular gas. The former is called spontaneous and the latter induced SF. The mass in the different phases of each region changes by the processes associated with the stellar formation and death by: the SF due to spontaneous fragmentation of gas in the halo; formation of gas clouds in the disk from the diffuse gas; induced SF in the disk due to the interaction between massive stars and gas clouds; and finally, the restitution of the diffuse gas associated to these process of cloud and star formation. In the halo, the star formation rate for the diffuse gas follows a Schmidt law with a power n = 1.5. In the disk, the stars form in two steps: first, molecular clouds are formed from the diffuse gas also following a Schmidt law with n=1.5 and a proportionality factor. Including a specific pattern of radial gas flows, the CEM is able to reproduce with success the peak in the SFR at 4 kpc (fig. 1).

scholarly journals The HI Content of Non-Isolated Galaxies

1990 ◽  
Vol 124 ◽  
pp. 175-182
Author(s):  
Anatoli V. Zasov
Keyword(s):  
Star Formation ◽  
Time Scale ◽  
Star Formation Rate ◽  
Massive Stars ◽  
Formation Rate ◽  
Interacting Galaxies ◽  
Gas Content ◽  
Disk Galaxies ◽  
Isolated Galaxies

It seems obvious that the evolution of star formation rate and hence of gas content in galaxies strongly depends on their environment. It reveals itself in particular in enhanced star formation or even in a strong burst of activity of massive stars often observed in an interacting galaxies. Nevertheless it should be noted that the time scale for the gas to be exhausted in these galaxies is unknown even approximately. To clarify a role of surroundings in the evolution of disk galaxies we should compare the HI content of isolated and non-isolated galaxies otherwise similar by their properties.

scholarly journals Positive feedback at the disc–halo interface

2020 ◽  
Vol 498 (1) ◽  
pp. 1140-1158
Author(s):  
Alexander Hobbs ◽  
Robert Feldmann
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Positive Feedback ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Galactic Disc ◽  
The Galaxy ◽  
History Of ◽  
Halo Gas ◽  
Cold Gas

ABSTRACT The flat star formation (SF) history of the Milky Way (MW) requires gas in the Galactic disc to be replenished, most likely from a reservoir outside the Galaxy. Such a replenishment may be achieved by a form of ‘positive’ feedback, whereby SF feedback creates a Galactic fountain cycle that collects and cools additional gas from the hot halo surrounding the Galaxy. In this paper, we present a model of this process for the MW. A section of the Galactic disc is allowed to form stars that subsequently explode as supernovae and send gas out into the hot halo. The gas that is sent out is colder than the hot halo gas and, as it mixes, the halo gas is cooled, providing fuel for further SF as the mixture falls back on to the Galactic disc. We find that this process can be sufficient to maintain a roughly constant cold gas mass in the MW over at least 3 Gyr. Our results further suggest that there is a positive feedback trend whereby increasing SF leads to an increase in the cold gas budget at average SF rates below $0.5 {\, {\rm M}_\odot}$ yr−1 and a negative feedback trend above this where further increasing the star formation rate leads to a decrease in the cold gas budget. We have constructed an analytical model for this that reproduces the data well and could have profound implications for galaxy evolution in feedback-dominated regimes.

scholarly journals A Model for Self-Regulating Star Formation

1987 ◽  
Vol 115 ◽  
pp. 548-550
Author(s):  
Tommy Wiklind
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Phenomenological Model ◽  
Star Formation Rate ◽  
Massive Stars ◽  
Formation Rate ◽  
Interacting Galaxies ◽  
Molecular Gas ◽  
Late Type ◽  
Star Forming

To model the nearly constant star formation rate, SFR, observed in most late-type galaxies (Gallagher et al. 1984), as well as the starbursting behaviour of some interacting galaxies (Joseph et al. 1984) we have developed a phenomenological model of the regulatory coupling between the density of the star forming part of the interstellar medium, i.e. molecular gas, and the rate of formation of massive stars.

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