scholarly journals A Reference Sample: ISM of the Most Isolated Galaxies

2004 ◽  
Vol 217 ◽  
pp. 220-221
Author(s):  
L. Verdes-Montenegro ◽  
J. Sulentic ◽  
D. Espada ◽  
S. Leon ◽  
U. Lisenfeld ◽  
...  
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Galaxy Evolution ◽  
Reference Sample ◽  
Control Sample ◽  
Evolution Of Galaxies ◽  
Isolated Galaxies ◽  
Internal Evolution

We are constructing the first complete unbiased control sample of the most isolated galaxies of the northern sky to serve as a template in the study of star formation and galaxy evolution in denser environments. Our goal is to compare and quantify the properties of different phases of the interstellar medium in this sample, as well as the level of star formation, both relevant parameters in the internal evolution of galaxies and strongly conditioned by the environment. To achieve this goal we are building a multiwavelength database for this sample to compare and quantify the properties of different phases of the ISM.

scholarly journals Spatially resolved signature of quenching in star-forming galaxies

2019 ◽  
Vol 490 (2) ◽  
pp. 2347-2366 ◽  
Author(s):  
Salvatore Quai ◽  
Lucia Pozzetti ◽  
Michele Moresco ◽  
Annalisa Citro ◽  
Andrea Cimatti ◽  
...  
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Galaxy Evolution ◽  
Spatial Information ◽  
Formation Rate ◽  
Radial Profile ◽  
Control Sample ◽  
Star Forming ◽  
Radial Profiles ◽  
Two Samples

ABSTRACT Understanding when, how, and where star formation ceased (quenching) within galaxies is still a critical subject in galaxy evolution studies. Taking advantage of the new methodology developed by Quai et al. to select recently quenched galaxies, we explored the spatial information provided by the IFU data to get critical insights on this process. In particular, we analyse 10 SDSS-IV MaNGA galaxies that show regions with low [O iii]/H α compatible with a recent quenching of the star formation. We compare the properties of these 10 galaxies with those of a control sample of 8 MaNGA galaxies with ongoing star formation in the same stellar mass, redshift, and gas-phase metallicity range. The quenching regions found are located between 0.5 and 1.1 effective radii from the centre. This result is supported by the analysis of the average radial profile of the ionization parameter, which reaches a minimum at the same radii, while the one of the star-forming sample shows an almost flat trend. These quenching regions occupy a total area between ∼ 15 and 45 per cent of our galaxies. Moreover, the average radial profile of the star formation rate surface density of our sample is lower and flatter than that of the control sample, at any radii, suggesting a systematic suppression of the star formation in the inner part of our galaxies. Finally, the radial profiles of gas-phase metallicity of the two samples have a similar slope and normalization. Our results cannot be ascribed to a difference in the intrinsic properties of the analysed galaxies, suggesting a quenching scenario more complicated than a simple inside-out quenching.

scholarly journals Molecular gas in galaxies: changing conditions from disks to starbursts

2015 ◽  
Vol 11 (S315) ◽  
pp. 199-206
Author(s):  
Christine D. Wilson
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Galaxy Evolution ◽  
Surface Density ◽  
Physical State ◽  
Active Galaxies ◽  
Molecular Gas ◽  
Central Question ◽  
Space Observatory ◽  
Nearby Galaxies

AbstractIn understanding galaxy evolution, one central question is how star formation is regulated in galaxies. Changes in star formation rates are likely tied to changes in the interstellar medium, particularly the molecular gas which is the fuel for star formation. I will discuss our recent results which use data from the Herschel Space Observatory, the Atacama Large Millimeter/submillimeter Array, and other telescopes to determine the typical density, temperature, and surface density of the molecular gas in various nearby galaxies. Comparing the properties of molecular gas in starburst and other active galaxies with more quiescent spiral disks provides some clues as to how changes in the physical state of the gas, such as mean density, can lead to enhanced star formation rates.

scholarly journals Gas Flows in Galaxies: the Relative Importance of Mergers and Bars.

2010 ◽  
Vol 6 (S277) ◽  
pp. 178-181
Author(s):  
Sara L. Ellison ◽  
David R. Patton ◽  
Preethi Nair ◽  
Luc Simard ◽  
J. Trevor Mendel ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Formation Rate ◽  
Control Sample ◽  
Central Star ◽  
Sloan Digital Sky Survey ◽  
Galaxy Interactions ◽  
Barred Galaxies ◽  
Isolated Galaxies ◽  
Stellar Masses

AbstractGalaxy-galaxy interactions and large scale galaxy bars are usually considered as the two main mechanisms for driving gas to the centres of galaxies. By using large samples of galaxy pairs and visually classified bars from the Sloan Digital Sky Survey (SDSS), we compare the relative efficiency of gas inflows from these two processes. We use two indicators of gas inflow: star formation rate (SFR) and gas phase metallicity, which are both measured relative to control samples. Whereas the metallicity of galaxy pairs is suppressed relative to its control sample of isolated galaxies, galaxies with bars are metal-rich for their stellar mass by 0.06 dex over all stellar masses. The SFRs of both the close galaxy pairs and the barred galaxies are enhanced by ~60%, but in the bars the enhancement is only seen at stellar masses M∗ > 1010 M⊙. Taking into account the relative frequency of bars and pairs, we estimate that at least three times more central star formation is triggered by bars than by interactions.

scholarly journals The elephant in the bathtub: when the physics of star formation regulate the baryon cycle of galaxies

2020 ◽  
Vol 500 (2) ◽  
pp. 2000-2011
Author(s):  
Jindra Gensior ◽  
J M Diederik Kruijssen
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
High Redshift ◽  
Formation Rate ◽  
Cosmic Time ◽  
Free Fall ◽  
Isolated Galaxies ◽  
The Galaxy ◽  
Galaxy Masses

ABSTRACT In simple models of galaxy formation and evolution, star formation is solely regulated by the amount of gas present in the galaxy. However, it has recently been shown that star formation can be suppressed by galactic dynamics in galaxies that contain a dominant spheroidal component and a low gas fraction. This ‘dynamical suppression’ is hypothesized to also contribute to quenching gas-rich galaxies at high redshift, but its impact on the galaxy population at large remains unclear. In this paper, we assess the importance of dynamical suppression in the context of gas regulator models of galaxy evolution through hydrodynamic simulations of isolated galaxies, with gas-to-stellar mass ratios of 0.01–0.20 and a range of galactic gravitational potentials from disc-dominated to spheroidal. Star formation is modelled using a dynamics-dependent efficiency per free-fall time, which depends on the virial parameter of the gas. We find that dynamical suppression becomes more effective at lower gas fractions and quantify its impact on the star formation rate as a function of gas fraction and stellar spheroid mass surface density. We combine the results of our simulations with observed scaling relations that describe the change of galaxy properties across cosmic time, and determine the galaxy mass and redshift range where dynamical suppression may affect the baryon cycle. We predict that the physics of star formation can limit and regulate the baryon cycle at low redshifts (z ≲ 1.4) and high galaxy masses (M* ≳ 3 × 1010 M⊙), where dynamical suppression can drive galaxies off the star formation main sequence.

Star formation and environment: a step in understanding the formation and evolution of local dwarf galaxies

2018 ◽  
Vol 14 (S344) ◽  
pp. 413-416
Author(s):  
Elena Sacchi ◽  
Michele Cignoni ◽  
Alessandra Aloisi ◽  
Monica Tosi
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Star Formation History ◽  
Star Forming ◽  
Star Forming Regions ◽  
Isolated Galaxies ◽  
Irregular Galaxies ◽  
Formation History ◽  
Formation And Evolution ◽  
The Many

AbstractWe present here the results obtained from studying the resolved stellar populations of two dwarf irregular galaxies in the nearby Universe. These galaxies, DDO 68 and NGC 4449, were studied within the Legacy ExtraGalactic UV Survey, an HST program aimed to uncover the many ways in which the star formation (SF) process occurs at different scales. Thanks to the deep photometry obtained in different bands (from λ2704 Å to λ8057 Å), we were able to connect the location and timescales of the star forming regions within the galaxies to merging and interaction with gas clouds and satellites, a crucial aspect of galaxy evolution, even in such small systems. From the color-magnitude diagrams of the analyzed galaxies we were able to recover their star formation history (up to ∼ 2 − 3 Gyr ago since we do not observe the oldest main sequence turn-off or horizontal branch, due to the systems’ distance), finding that the SF never really stopped, but proceeded continuously even with the succession of high and low activity. The time intervals where we find higher SF rates in the two galaxies well agree with the dynamical timescales of previous interactions events, which might represent a major channel for triggering the SF in relatively isolated galaxies.

scholarly journals Star Formation in a Magnitude Limited Sample of Interacting Galaxies

1996 ◽  
Vol 171 ◽  
pp. 344-344
Author(s):  
Nils Bergvall ◽  
Eija Laurikainen ◽  
Susanne Aalto ◽  
Lennart Johansson
Keyword(s):  
Star Formation ◽  
Control Sample ◽  
Central Area ◽  
Interacting Galaxies ◽  
Moderate Increase ◽  
Limited Sample ◽  
Merging Galaxies ◽  
Near Ir ◽  
Isolated Galaxies ◽  
Star Formation Activity

We report on optical/near-IR spectroscopy and photometry of a magnitude limited sample of interacting pairs and merging galaxies and a control sample of apparently isolated galaxies (1,2). All observations were carried out at ESO, La Silla. When compared to the control sample, the interacting galaxies show only a moderate increase of star formation activity, in the central area typically a factor 2-3. Starburst activity seems to be very rare. Ongoing CO observations (Aalto, Horellou, Booth, Wiklind, Bergvall) indicate that these objects are not particularly rich in molecular gas. The interacting/merging galaxies have relatively high optical luminosities and high FIR luminosities and temperatures but these parameters are not correlated with other star formation signatures. We conclude that the interacting and merging galaxies in this sample, from the global star formation aspect, do not differ dramatically from scaled up versions of normal, isolated galaxies. This could suggest that many of the most lumino components in interacting pairs could originate from multiple ‘quiet’ mergers.

scholarly journals Evolution of Galaxies with Periodic Star Formation

1987 ◽  
Vol 115 ◽  
pp. 691-699
Author(s):  
Satoru Ikeuchi
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Molecular Clouds ◽  
Gravitational Instability ◽  
Giant Molecular Clouds ◽  
Evolution Of Galaxies

Interchange processes in the interstellar medium, which is composed of diffuse gas, small clouds and giant molecular clouds are examined. It is stressed that the formation of giant molecular clouds through gravitational instability of a cloud ensemble leads to periodic star formation. The evolution of galaxies with such periodic star formation episodes is studied, especially paying attention to the effect of gas infall.

scholarly journals The Metallicity Evolution of Galaxies through the Cosmic Epochs

2010 ◽  
Vol 6 (S277) ◽  
pp. 170-173
Author(s):  
R. Maiolino
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Optical Observations ◽  
Fundamental Relation ◽  
Evolution Of Galaxies ◽  
Spatially Resolved ◽  
Near Ir ◽  
Distant Galaxies ◽  
Central Regions ◽  
Low Metallicity

AbstractWe have found that local galaxies follow a very tight relation between gas metallicity, stellar mass and SFR, suggesting that their evolution is characterized by a long standing equilibrium between gas inflows, outflows and star formation. Surprisingly, even distant galaxies, out to z < 2.5, follow the same relation, suggesting that the same dominant mechanism of galaxy evolution is in place at any epoch, out to z < 2.5. However, by using deep near-IR spectroscopy (probing optical nebular lines at high-z), we find that galaxies at z > 3 deviate from such fundamental relation, by being significantly more metal poor. Spatially resolved metallicity maps of z > 3 disk galaxies reveal that they are characterized by central regions with low metallicity associated with the peak of star formation, indicating that the latter is due to massive inflow of pristine gas that both boosts star formation and dilutes the gas metallicity. Overall these results suggest that the metallicity evolution of galaxies at z > 3 is due to an excess of gas inflow at such early epochs, as expected by some recent models. Finally, we investigate the metallicity of merging systems, both locally and at high-z. By exploiting recent Herschel data, we have found that in these systems the dust content directly measured through the FIR-submm data is much higher than inferred from the metallicity measured through the optical nebular lines. The latter result suggests that, in these heavily obscured systems, optical observations only probe the outer, less enriched regions and are not representative of the bulk of the metal content.

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