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 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.

Two of the most Metal-deficient Stars

1977 ◽  
Vol 3 (2) ◽  
pp. 144-145 ◽  
Author(s):  
M. S. Bessel
Keyword(s):  
Star Formation ◽  
Metal Content ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Individual Metal ◽  
The Galaxy ◽  
History Of

The metal content of stars (and galaxies) is of great interest as it relates to the theories of element formation, and through these to the history of our galaxy, the frequency of supernovae, the star formation rate and even the quasar rate. The kinematics and metallicity of stars have been correlated in a theory of formation of the galaxy by Eggen et al. (1962). Alternate theories (Unsold 1969) have also been proposed. Much work has gone into isolating individual metal deficient stars and determining their abundances, and also the abundances for stars in clusters.

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.

scholarly journals The evolution of the mass-metallicity relations from the VANDELS survey and the gaea Semi-Analytic model

2021 ◽  
Author(s):  
Fabio Fontanot ◽  
Antonello Calabró ◽  
Margherita Talia ◽  
Filippo Mannucci ◽  
Marco Castellano ◽  
...  
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Galaxy Evolution ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Analytic Model ◽  
Redshift Range ◽  
Model Predictions ◽  
The Galaxy ◽  
Lower Redshift

Abstract In this work, we study the evolution of the mass-metallicity relations (MZRs) as predicted by the GAlaxy Evolution and Assembly (gaea) semi-analytic model. We contrast these predictions with recent results from the VANDELS survey, that allows us to expand the accessible redshift range for the stellar MZR up to z ∼ 3.5. We complement our study by considering the evolution of the gas-phase MZR in the same redshift range. We show that gaea is able to reproduce the observed evolution of the z < 3.5 gas-phase MZR and z < 0.7 stellar MZR, while it overpredicts the stellar metallicity at z ∼ 3.5. Furthermore, gaea also reproduces the so-called fundamental metallicity relation (FMR) between gas-phase metallicity, stellar mass and star formation rate (SFR). In particular, the gas-phase FMR in gaea is already in place at z ∼ 5 and shows almost no evolution at lower redshift. gaea predicts the existence of a stellar FMR, that is, however, characterized by a relevant redshift evolution, although its shape follows closely the gas-phase FMR. We also report additional unsolved tensions between model and data: the overall normalization of the predicted MZR agrees with observations only within ∼0.1 dex; the largest discrepancies are seen at z ∼ 3.5 where models tend to slightly overpredict observed metallicities; the slope of the predicted MZR at fixed SFR is too steep below a few M⊙ yr−1. Finally, we provide model predictions for the evolution of the MZRs at higher redshifts, that would be useful in the context of future surveys, like those that will be performed with JWST.

The Galaxy Evolution Explorer - Early Data

2005 ◽  
Vol 216 ◽  
pp. 221-229 ◽  
Author(s):  
Christopher Martin ◽  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Formation Rate ◽  
Early Data ◽  
Nearby Galaxy ◽  
Deep Imaging ◽  
Explorer Mission ◽  
Sky Survey ◽  
The Galaxy ◽  
History Of

We report on early data from the Galaxy Evolution Explorer (GALEX), a NASA Explorer Mission launched on April 28, with a nominal mission start of June 19. GALEX is performing the first space UV sky-survey, including imaging and grism surveys in two bands (1350–1750 Å and 1750–2800 Å). The surveys include an all-sky imaging survey (limit AB∼20–21), a medium imaging survey of 1000 sq. deg (limit AB∼23.5), a deep imaging survey of 100 deg2 (limit AB∼25.5), and a nearby galaxy survey. Spectroscopic grism surveys (R=100–300) will be performed with various depths and sky coverage. Many targets overlap existing or planned surveys, including SDSS, DEEP, NOAODWS, VIRMOS, SWIRE, SINGS, SIRTF-GTO, Chandra, and HST/ACS. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the redshift range 0<z<2. The GALEX mission will include a Guest Investigator program for primary observations and supporting data analysis. This will support a wide variety of investigations made possible by the first UV sky survey.

scholarly journals The Sagittarius Dwarf Galaxy Survey (SDGS): Constraints on the Star Formation History of the Sgr dSph

1999 ◽  
Vol 192 ◽  
pp. 121-128
Author(s):  
M. Bellazzini ◽  
F. R. Ferraro ◽  
R. Buonanno
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Star Formation History ◽  
Full Potential ◽  
Chemical Enrichment ◽  
Formation History ◽  
The Galaxy ◽  
History Of

The main characteristics of a wide photometric survey of the Sgr dwarf spheroidal galaxy are briefly presented. V and I photometry has been obtained for ~90000 stars toward Sgr and for ~9000 stars in a region devoid of Sgr stars (for decontamination purposes).The full potential of this large database is far from being completely explored. Here we present only preliminary results from the analysis of statistically decontaminated Color Magnitude Diagrams, trying to set a scheme of the Star Formation History of the Sgr Galaxy. A scenario is proposed in which star formation in Sgr began very early and lasted for several Gyr, with progressive chemical enrichment of the Inter-Stellar Medium (ISM). Nearly 8 Gyr ago the star formation rate abruptly decreased, perhaps in coincidence with the event that led to the gas depletion of the galaxy. A very small rate of star formation continued until relatively recent times (~ 1 Gyr ago).

scholarly journals Cosmological simulations of low-mass galaxies: some potential issues

2010 ◽  
Vol 6 (S270) ◽  
pp. 503-506
Author(s):  
Pedro Colín ◽  
Vladimir Avila-Reese ◽  
Octavio Valenzuela
Keyword(s):  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Mass Fraction ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Stellar Mass ◽  
The Galaxy ◽  
Low Mass

AbstractCosmological Adaptive Mesh Refinement simulations are used to study the specific star formation rate (sSFR=SSF/Ms) history and the stellar mass fraction, fs=Ms/MT, of small galaxies, total masses MT between few × 1010 M⊙ to few ×1011 M⊙. Our results are compared with recent observational inferences that show the so-called “downsizing in sSFR” phenomenon: the less massive the galaxy, the higher on average is its sSFR, a trend seen at least since z ~ 1. The simulations are not able to reproduce this phenomenon, in particular the high inferred values of sSFR, as well as the low values of fs constrained from observations. The effects of resolution and sub-grid physics on the SFR and fs of galaxies are discussed.

scholarly journals MUSE Analysis of Gas around Galaxies (MAGG) – II: metal-enriched halo gas around z ∼ 1 galaxies

2020 ◽  
Vol 499 (4) ◽  
pp. 5022-5046 ◽  
Author(s):  
Rajeshwari Dutta ◽  
Michele Fumagalli ◽  
Matteo Fossati ◽  
Emma K Lofthouse ◽  
J Xavier Prochaska ◽  
...  
Keyword(s):  
Cross Section ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Dominant Factor ◽  
Isolated Galaxies ◽  
The Galaxy ◽  
Group Members ◽  
Halo Gas ◽  
Parameter Relation ◽  
Complex Distribution

ABSTRACT We present a study of the metal-enriched cool halo gas traced by Mg ii absorption around 228 galaxies at z ∼ 0.8–1.5 within 28 quasar fields from the MUSE Analysis of Gas around Galaxies survey. We observe no significant evolution in the Mg ii equivalent width versus impact parameter relation and in the Mg ii covering fraction compared to surveys at z ≲ 0.5. The stellar mass, along with distance from galaxy centre, appears to be the dominant factor influencing the Mg ii absorption around galaxies. With a sample that is 90 per cent complete down to a star formation rate of ≈0.1 $\rm M_\odot yr^{-1}$ and up to impact parameters ≈250–350 kpc from quasars, we find that the majority ($67^{+12}_{-15}$ per cent or 14/21) of the Mg ii absorption systems are associated with more than one galaxy. The complex distribution of metals in these richer environments adds substantial scatter to previously reported correlations. Multiple galaxy associations show on average five times stronger absorption and three times higher covering fraction within twice the virial radius than isolated galaxies. The dependence of Mg ii absorption on galaxy properties disfavours the scenario in which a widespread intragroup medium dominates the observed absorption. This leaves instead gravitational interactions among group members or hydrodynamic interactions of the galaxy haloes with the intragroup medium as favoured mechanisms to explain the observed enhancement in the Mg ii absorption strength and cross-section in rich environments.

scholarly journals SDSS J114818.18-013823.7: Forming Compact Dwarf Galaxy through the Dwarf-Dwarf Merger

2021 ◽  
Vol 7 (2) ◽  
pp. 49-57
Author(s):  
D. N. Chhatkuli ◽  
S. Paudel ◽  
A. K. Gautam ◽  
B. Aryal
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Absolute Magnitude ◽  
Spectroscopic Properties ◽  
Normal Galaxies ◽  
Star Formation Activity ◽  
The Galaxy

We studied the spectroscopic properties of the low redshift (z = 0.0130) interacting dwarf galaxy SDSS J114818.18-013823.7. It is a compact galaxy of half-light radius 521 parsec. It’s r-band absolute magnitude is -16.71 mag. Using a publicly available optical spectrum from the Sloan Sky Survey data archive, we calculated star-formation rate, emission line metallicity, and dust extinction of the galaxy. Star formation rate (SFR) due to Hα is found to be 0.118 Mʘ year-1 after extinction correction. The emission-line metallicity, 12+log(O/H), is 8.13 dex. Placing these values in the scaling relation of normal galaxies, we find that SDSS J114818.18-013823.7 is a significant outlier from both size-magnitude relation and SFR-B-band absolute relation. Although SDSS J114818.18-013823.7 possess enhance rate of star-formation, the current star-formation activity can persist several Giga years in the future at the current place and it remains compact.

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