scholarly journals Gas accretion regulates the scatter of the mass–metallicity relation

2020 ◽  
Vol 498 (3) ◽  
pp. 3215-3227
Author(s):  
Gabriella De Lucia ◽  
Lizhi Xie ◽  
Fabio Fontanot ◽  
Michaela Hirschmann
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Formation Rate ◽  
Gas Content ◽  
Stellar Feedback ◽  
Accretion Rates ◽  
The Galaxy ◽  
Gas Cooling ◽  
Gas Accretion ◽  
Cold Gas

ABSTRACT In this paper, we take advantage of the GAlaxy Evolution and Assembly (GAEA) semi-analytic model to analyse the origin of secondary dependencies in the local galaxy mass–gas metallicity relation. Our model reproduces quite well the trends observed in the local Universe as a function of galaxy star formation rate and different gas-mass phases. We show that the cold gas content (whose largest fraction is represented by the atomic gas phase) can be considered as the third parameter governing the scatter of the predicted mass–metallicity relation, in agreement with the most recent observational measurements. The trends can be explained with fluctuations of the gas accretion rates: a decrease of the gas supply leads to an increase of the gas metallicity due to star formation, while an increase of the available cold gas leads to a metallicity depletion. We demonstrate that the former process is responsible for offsets above the mass–metallicity relation, while the latter is responsible for deviations below the mass–metallicity relation. In low- and intermediate-mass galaxies, these negative offsets are primarily determined by late gas cooling dominated by material that has been previously ejected due to stellar feedback.

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 Scaling relations and baryonic cycling in local star-forming galaxies

2020 ◽  
Vol 643 ◽  
pp. A180
Author(s):  
L. K. Hunt ◽  
C. Tortora ◽  
M. Ginolfi ◽  
R. Schneider
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Dwarf Galaxies ◽  
Formation Rate ◽  
Gas Content ◽  
Scaling Relations ◽  
Star Forming ◽  
Atomic Gas ◽  
Mass Assembly ◽  
Gas Accretion

Assessments of the cold-gas reservoir in galaxies are a cornerstone for understanding star-formation processes and the role of feedback and baryonic cycling in galaxy evolution. Here we exploit a sample of 392 galaxies (dubbed MAGMA, Metallicity and Gas for Mass Assembly), presented in a recent paper, to quantify molecular and atomic gas properties across a broad range in stellar mass, Mstar, from ∼107 − 1011 M⊙. First, we find the metallicity (Z) dependence of the conversion factor for CO luminosity to molecular H2 mass αCO to be shallower than previous estimates, with αCO  ∝  (Z/Z⊙)−1.55. Second, molecular gas mass MH2 is found to be strongly correlated with Mstar and star-formation rate (SFR), enabling predictions of MH2 good to within ∼0.2 dex; analogous relations for atomic gas mass MHI and total gas mass Mgas are less accurate, ∼0.4 dex and ∼0.3 dex, respectively. Indeed, the behavior of atomic gas mass MHI in MAGMA scaling relations suggests that it may be a third, independent variable that encapsulates information about the circumgalactic environment and gas accretion. If Mgas is considered to depend on MHI, together with Mstar and SFR, we obtain a relation that predicts Mgas to within ∼0.05 dex. Finally, the analysis of depletion times and the scaling of MHI/Mstar and MH2/Mstar over three different mass bins suggests that the partition of gas and the regulation of star formation through gas content depends on the mass regime. Dwarf galaxies (Mstar  ≲  3 × 109 M⊙) tend to be overwhelmed by (H I) accretion, and despite short τH2 (and thus presumably high star-formation efficiency), star formation is unable to keep up with the gas supply. For galaxies in the intermediate Mstar “gas-equilibrium” bin (3 × 109 M⊙ ≲ Mstar ≲3 × 1010 M⊙), star formation proceeds apace with gas availability, and H I and H2 are both proportional to SFR. In the most massive “gas-poor, bimodality” regime (Mstar ≳ 3 × 1010 M⊙), H I does not apparently participate in star formation, although it generally dominates in mass over H2. Our results confirm that atomic gas plays a key role in baryonic cycling, and is a fundamental ingredient for current and future star formation, especially in dwarf galaxies.

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 Mentari: A pipeline to model the galaxy SED using semi analytic models

2019 ◽  
Vol 15 (S341) ◽  
pp. 119-123
Author(s):  
Dian Triani ◽  
Darren Croton ◽  
Manodeep Sinha
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Spectral Energy Distribution ◽  
Cosmic Time ◽  
Spectral Energy ◽  
Chemical Enrichment ◽  
The Galaxy ◽  
History Of ◽  
Gas Accretion ◽  
Analytic Models

AbstractWe build a theoretical picture of how the light from galaxies evolves across cosmic time. In particular, we predict the evolution of the galaxy spectral energy distribution (SED) by carefully integrating the star formation and metal enrichment histories of semi-analytic model (SAM) galaxies and combining these with stellar population synthesis models which we call mentari. Our SAM combines prescriptions to model the interplay between gas accretion, star formation, feedback process, and chemical enrichment in galaxy evolution. From this, the SED of any simulated galaxy at any point in its history can be constructed and compared with telescope data to reverse engineer the various physical processes that may have led to a particular set of observations. The synthetic SEDs of millions of simulated galaxies from mentari can cover wavelengths from the far UV to infrared, and thus can tell a near complete story of the history of galaxy evolution.

scholarly journals Interstellar Medium and Star Formation in Dwarf Galaxies

2018 ◽  
Vol 14 (S344) ◽  
pp. 233-239
Author(s):  
Alberto D. Bolatto
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Dwarf Galaxies ◽  
Gas Content ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Cold Gas

AbstractThis is a brief review of our understanding of the properties of the interstellar medium (ISM) in dwarf galaxies in connection to their star formation activity. What are the dominant phases of the ISM in these objects? How do the properties of these phases depend on the galaxy properties? What do we know about their cold gas content and its link to star formation activity? Does star formation proceed differently in these galaxies? How does star formation feedback operate in dwarf galaxies? The availability of observations from space-based facilities such as FUSE, Spitzer, Herschel, and Fermi, as well as observatories such as SOFIA and ALMA, is allowing us to make significant strides in our understanding of these questions.

scholarly journals Local starbursts seen when the Universe was 2–4 Gyr old

2009 ◽  
Vol 5 (S266) ◽  
pp. 499-499
Author(s):  
S. M. Petty ◽  
D. F. de Mello ◽  
J. P. Gardner ◽  
J. S. Gallagher
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Rest Frame ◽  
Formation Rate ◽  
Starburst Galaxies ◽  
Spectral Energy ◽  
Multiple Star ◽  
Star Forming ◽  
The Galaxy ◽  
The Universe

AbstractWe explore the multiwavelength properties of three nearby starburst galaxies: NGC 3079, NGC 7673, and Mrk 08. We established that each of these galaxies has similar rest-frame far-ultraviolet (FUV) morphologies as Lyman-break galaxies (LBGs) at z ~ 1.5 and 4, when the age of the Universe was ~ 4.3 and ~ 1.6 Gyr, respectively. LBGs are at an important stage in galaxy evolution when the Universe had a peak in the star-formation-rate density. Many LBGs are primarily composed of star-forming clumps, i.e., stellar clusters, with a significant lack of older stellar populations. Here, we present the comparison of the spectral-energy distributions (SEDs) of three nearby starburst galaxies with those of typical LBGs. From our nearby sample, each object has been artificially redshifted to observe what the galaxies would look like at z ~ 1 to 4 in the rest-frame FUV. NGC 3079 is an edge-on Seyfert 2 galaxy. It has a bright bulge and is interacting with two other galaxies, with extended Hi only along NGC 3079. The redshifting process changes its appearance, so that at high z it looks like a chain galaxy with multiple knots of star formation and no bulge. NGC 7673 has extended Hi and the star formation is mostly within the inner optical region in the multiple star-forming clumps defining the galaxy morphology. In the FUV, the galaxy looks highly compact with little detail resolved. As it is artificially redshifted, the galaxy continues to look more spherical. Mrk 8 is a merging pair, with the two galaxies observable in the visible spectrum. It is classified as a Wolf–Rayet galaxy, which suggests a very young burst, and is composed of several large star-forming regions. The FUV image does not resolve the separate galaxies, and the appearance remains similar for each redshift. We use the Gini coefficient, M20, and the Sérsic index to quantify the morphologies. The SEDs of the objects have similarities with LBG stellar population models. Because these local galaxies can be studied in more detail, they act as a bridge between nearby observations of starburst galaxies and high-z starburst galaxies such as LBGs.

scholarly journals Ejective and preventative: the IllustrisTNG black hole feedback and its effects on the thermodynamics of the gas within and around galaxies

2020 ◽  
Vol 499 (1) ◽  
pp. 768-792 ◽  
Author(s):  
Elad Zinger ◽  
Annalisa Pillepich ◽  
Dylan Nelson ◽  
Rainer Weinberger ◽  
Rüdiger Pakmor ◽  
...  
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Massive Galaxies ◽  
Star Forming ◽  
The Galaxy ◽  
Gas Cooling ◽  
Galaxy Population ◽  
Gas Accretion ◽  
Stellar Masses ◽  
Low Entropy

ABSTRACT Supermassive black holes (SMBHs) that reside at the centres of galaxies can inject vast amounts of energy into the surrounding gas and are thought to be a viable mechanism to quench star formation in massive galaxies. Here, we study the $10^{9-12.5}\, \mathrm{M_\odot }$ stellar mass central galaxy population of the IllustrisTNG simulation, specifically the TNG100 and TNG300 volumes at z = 0, and show how the three components – SMBH, galaxy, and circumgalactic medium (CGM) – are interconnected in their evolution. We find that gas entropy is a sensitive diagnostic of feedback injection. In particular, we demonstrate how the onset of the low-accretion black hole (BH) feedback mode, realized in the IllustrisTNG model as a kinetic, BH-driven wind, leads not only to star formation quenching at stellar masses $\gtrsim 10^{10.5}\, \mathrm{M_\odot }$ but also to a change in thermodynamic properties of the (non-star-forming) gas, both within the galaxy and beyond. The IllustrisTNG kinetic feedback from SMBHs increases the average gas entropy, within the galaxy and in the CGM, lengthening typical gas cooling times from $10\!-\!100\, \mathrm{Myr}$ to $1\!-\!10\, \mathrm{Gyr}$, effectively ceasing ongoing star formation and inhibiting radiative cooling and future gas accretion. In practice, the same active galactic nucleus (AGN) feedback channel is simultaneously ‘ejective’ and ‘preventative’ and leaves an imprint on the temperature, density, entropy, and cooling times also in the outer reaches of the gas halo, up to distances of several hundred kiloparsecs. In the IllustrisTNG model, a long-lasting quenching state can occur for a heterogeneous CGM, whereby the hot and dilute CGM gas of quiescent galaxies contains regions of low-entropy gas with short cooling times.

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.

scholarly journals Unravelling the enigmatic ISM conditions in Minkowski’s object

2020 ◽  
Vol 499 (4) ◽  
pp. 4940-4960
Author(s):  
Henry R M Zovaro ◽  
Robert Sharp ◽  
Nicole P H Nesvadba ◽  
Lisa Kewley ◽  
Ralph Sutherland ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Theoretical Models ◽  
Strong Line ◽  
Valuable Insight ◽  
Jet Interaction ◽  
Star Forming ◽  
The Galaxy

ABSTRACT Local examples of jet-induced star formation lend valuable insight into its significance in galaxy evolution and can provide important observational constraints for theoretical models of positive feedback. Using optical integral field spectroscopy, we present an analysis of the ISM conditions in Minkowski’s object (z = 0.0189), a peculiar star-forming dwarf galaxy located in the path of a radio jet from the galaxy NGC 541. Full spectral fitting with ppxf indicates that Minkowski’s object primarily consists of a young stellar population $\sim \! 10\, \rm Myr$ old, confirming that the bulk of the object’s stellar mass formed during a recent jet interaction. Minkowski’s object exhibits line ratios largely consistent with star formation, although there is evidence for a low level ($\lesssim \! 15 \, \rm per \, cent$) of contamination from a non-stellar ionizing source. Strong-line diagnostics reveal a significant variation in the gas-phase metallicity within the object, with $\log \left(\rm O / H \right) + 12$ varying by $\sim \! 0.5\, \rm dex$, which cannot be explained by in-situ star formation, an enriched outflow from the jet, or enrichment of gas in the stellar bridge between NGC 541 and NGC 545/547. We hypothesize that Minkowski’s object either (i) was formed as a result of jet-induced star formation in pre-existing gas clumps in the stellar bridge, or (ii) is a gas-rich dwarf galaxy that is experiencing an elevation in its star formation rate due to a jet interaction, and will eventually redden and fade, becoming an ultradiffuse galaxy as it is processed by the cluster.

scholarly journals Evolution of Dwarf Galaxies in the Centaurus A Group

2007 ◽  
Vol 3 (S244) ◽  
pp. 326-330 ◽  
Author(s):  
L. Makarova ◽  
D. Makarov
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Dwarf Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
The Galaxy ◽  
Probable Origin ◽  
Centaurus A ◽  
Environmental Dependence

AbstractWe consider the star formation properties of dwarf galaxies in the Cen A group observed within our HST/ACS projects number 9771 and 10235. We model color-magnitude diagrams of the galaxies under consideration and measure star formation rate and metallicity dependence on time. We study the environmental dependence of the galaxy evolution and probable origin of the dwarf galaxies in the group.

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