scholarly journals Anemic Galaxies: Evidence for a Threshold in Star Formation Processes

1987 ◽  
Vol 115 ◽  
pp. 633-633
Author(s):  
B. Guiderdoni
Keyword(s):  
Star Formation ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Critical Value ◽  
Virgo Cluster ◽  
Disk Galaxies ◽  
Formation Processes ◽  
The Galaxy ◽  
Gas Consumption

From a sample of Virgo Cluster and “field” disk galaxies, it is shown that a critical value of the HI surface density discriminates between RDDO anemic and “healthy” spirals. Below this threshold, at least massive stars do not form any more and the galaxy gets the anemic appearance. The influence of the HI content on the global star formation rate is discussed in the context of present models (Elmegreen 1979, Seiden and Gerola 1979, Dopita 1985), as well as the fate of disks in cluster and “field” environments. The existence of this threshold is an issue for the problem caused by the short gas consumption time scales derived from the observations of spiral galaxies.

scholarly journals Infrared Emission from Barred Spiral Galaxies

1996 ◽  
Vol 157 ◽  
pp. 54-62
Author(s):  
Tim G. Hawarden ◽  
J. H. Huang ◽  
Q. S. Gu
Keyword(s):  
Star Formation ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Infrared Emission ◽  
Stellar Radiation ◽  
The Galaxy ◽  
Barred Spiral Galaxies ◽  
Star Formation Regions ◽  
Ir Emission

AbstractAmongst relatively undisturbed spiral galaxies of type ≤ Sc barred morphology is unquestionably associated with powerful mid- and Far-IR emission. On the other hand, even amongst early type galaxies, those with LFIR/LB < 1/3 exhibit no association of high relative FIR luminosity with barred morphology, but some association of IR colors resembling those of star formation regions (SFRs). Amongst systems with LFIR/LB < 0.1 this ratio may be anti-correlated with barredness. It appears that enhanced IR emission from those galaxies whose star formation rate is currently elevated by the the bar translates them into the group with higher FIR-to-optical luminosity ratios. Depletion of extended nearnuclear gas and dust, once the bar has swept up the currently-available supplies, may reduce the fraction of the background stellar radiation field which can be converted to FIR radiation in the inner, most luminous parts of the galaxy. Thus, after the starburst has subsided, such galaxies may be less FIR-luminous than unbarred systems. Several uncertainties remain: it is still not clear whether barred morphology is a necessary condition for the generation of a starburst in an otherwise undisturbed galaxy, while evidence as to the effect of differing bar strengths is conflicting.

scholarly journals Bar quenching in gas-rich galaxies

2018 ◽  
Vol 609 ◽  
pp. A60 ◽  
Author(s):  
S. Khoperskov ◽  
M. Haywood ◽  
P. Di Matteo ◽  
M. D. Lehnert ◽  
F. Combes
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Turbulent Energy ◽  
Rapid Quenching ◽  
Disk Galaxies ◽  
The Galaxy ◽  
Formation Efficiency ◽  
Bar Formation

Galaxy surveys have suggested that rapid and sustained decrease in the star-formation rate (SFR), “quenching”, in massive disk galaxies is frequently related to the presence of a bar. Optical and near-IR observations reveal that nearly 60% of disk galaxies in the local universe are barred, thus it is important to understand the relationship between bars and star formation in disk galaxies. Recent observational results imply that the Milky Way quenched about 9–10 Gyr ago, at the transition between the cessation of the growth of the kinematically hot, old, metal-poor thick disk and the kinematically colder, younger, and more metal-rich thin disk. Although perhaps coincidental, the quenching episode could also be related to the formation of the bar. Indeed the transfer of energy from the large-scale shear induced by the bar to increasing turbulent energy could stabilize the gaseous disk against wide-spread star formation and quench the galaxy. To explore the relation between bar formation and star formation in gas rich galaxies quantitatively, we simulated gas-rich disk isolated galaxies. Our simulations include prescriptions for star formation, stellar feedback, and for regulating the multi-phase interstellar medium. We find that the action of stellar bar efficiently quenches star formation, reducing the star-formation rate by a factor of ten in less than 1 Gyr. Analytical and self-consistent galaxy simulations with bars suggest that the action of the stellar bar increases the gas random motions within the co-rotation radius of the bar. Indeed, we detect an increase in the gas velocity dispersion up to 20−35 km s-1 at the end of the bar formation phase. The star-formation efficiency decreases rapidly, and in all of our models, the bar quenches the star formation in the galaxy. The star-formation efficiency is much lower in simulated barred compared to unbarred galaxies and more rapid bar formation implies more rapid quenching.

scholarly journals Galaxy And Mass Assembly (GAMA): properties and evolution of red spiral galaxies

2019 ◽  
Vol 491 (1) ◽  
pp. 398-408 ◽  
Author(s):  
Smriti Mahajan ◽  
Kriti Kamal Gupta ◽  
Rahul Rana ◽  
M J I Brown ◽  
S Phillipps ◽  
...  
Keyword(s):  
Star Formation ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Direct Consequence ◽  
Morphological Transformation ◽  
The Galaxy ◽  
Long Time ◽  
Inclination Angles ◽  
Mass Assembly

ABSTRACT We use multiwavelength data from the Galaxy And Mass Assembly (GAMA) survey to explore the cause of red optical colours in nearby (0.002 < z < 0.06) spiral galaxies. We show that the colours of red spiral galaxies are a direct consequence of some environment-related mechanism(s) that has removed dust and gas, leading to a lower star formation rate. We conclude that this process acts on long time-scales (several Gyr) due to a lack of morphological transformation associated with the transition in optical colour. The specific star formation rate (sSFR) and dust-to-stellar mass ratio of red spiral galaxies is found to be statistically lower than blue spiral galaxies. On the other hand, red spirals are on average 0.9 dex more massive, and reside in environments 2.6 times denser than their blue counterparts. We find no evidence of excessive nuclear activity, or higher inclination angles to support these as the major causes for the red optical colours seen in ≳47 per cent of all spirals in our sample. Furthermore, for a small subsample of our spiral galaxies that are detected in H i, we find that the SFR of gas-rich red spiral galaxies is lower by ∼1 dex than their blue counterparts.

scholarly journals Optical Studies of Star Formation in Normal Spiral Galaxies: Radial Characteristics

1992 ◽  
Vol 45 (4) ◽  
pp. 395
Author(s):  
Stuart Ryder
Keyword(s):  
Star Formation ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Optical Studies ◽  
Ccd Imaging ◽  
The Past ◽  
Show Evidence ◽  
First Results ◽  
Gas Consumption

First results of a new, homogeneous CCD imaging survey of nearby southern spiral galaxies in V, I and Ha are presented. Elliptical aperture photometry has been used to determine the deprojected surface brightnesses as a function of galactocentric radius, and thus to trace the past and present star formation behaviour. From a sub-sample of nine mainly barred spirals, we find a couple of notable trends. Firstly, nearly all of the barred spirals show evidence of significant levels of ongoing star formation in the bulge, probably fed by gas inflow along the bar. Secondly, the disk Ha profiles are quite shallow compared with the broadband exponential disks, implying a relative insensitivity of the current star formation rate to the surface density of stars already formed. In both the bulge and the disk, the gas consumption timescales are such as to require gas replenishment, e.g. by radial inflow.

scholarly journals Molecular Clouds and Star Formation Rate in Disk Galaxies

2016 ◽  
Vol 25 (3) ◽  
Author(s):  
E. O. Vasiliev ◽  
S. A. Khoperskov ◽  
A. V. Khoperskov
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Disk Galaxies

AbstractWe use

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 CHANG-ES

2018 ◽  
Vol 611 ◽  
pp. A72 ◽  
Author(s):  
Marita Krause ◽  
Judith Irwin ◽  
Theresa Wiegert ◽  
Arpad Miskolczi ◽  
Ancor Damas-Segovia ◽  
...  
Keyword(s):  
Star Formation ◽  
Wind Velocity ◽  
Surface Density ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Scale Height ◽  
Radio Continuum ◽  
Frequency Bands

Aim. The vertical halo scale height is a crucial parameter to understand the transport of cosmic-ray electrons (CRE) and their energy loss mechanisms in spiral galaxies. Until now, the radio scale height could only be determined for a few edge-on galaxies because of missing sensitivity at high resolution.Methods. We developed a sophisticated method for the scale height determination of edge-on galaxies. With this we determined the scale heights and radial scale lengths for a sample of 13 galaxies from the CHANG-ES radio continuum survey in two frequency bands.Results. The sample average values for the radio scale heights of the halo are 1.1 ± 0.3 kpc in C-band and 1.4 ± 0.7 kpc in L-band. From the frequency dependence analysis of the halo scale heights we found that the wind velocities (estimated using the adiabatic loss time) are above the escape velocity. We found that the halo scale heights increase linearly with the radio diameters. In order to exclude the diameter dependence, we defined a normalized scale height h˜ which is quite similar for all sample galaxies at both frequency bands and does not depend on the star formation rate or the magnetic field strength. However, h˜ shows a tight anticorrelation with the mass surface density.Conclusions. The sample galaxies with smaller scale lengths are more spherical in the radio emission, while those with larger scale lengths are flatter. The radio scale height depends mainly on the radio diameter of the galaxy. The sample galaxies are consistent with an escape-dominated radio halo with convective cosmic ray propagation, indicating that galactic winds are a widespread phenomenon in spiral galaxies. While a higher star formation rate or star formation surface density does not lead to a higher wind velocity, we found for the first time observational evidence of a gravitational deceleration of CRE outflow, e.g. a lowering of the wind velocity from the galactic disk.

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.

scholarly journals Environmental Effects on the ISM and Star Formation Properties of Nearby Spiral Galaxies

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Angus Mok ◽  
Christine Wilson
Keyword(s):  
Star Formation ◽  
Environmental Effects ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Molecular Gas ◽  
Turbulent Pressure ◽  
Cluster Environment ◽  
Gas Properties

AbstractWe studied molecular gas properties in a sample of 98 Hi - flux selected spiral galaxies within ~ 25 Mpc using the CO J = 3 − 2 line, observed with the JCMT, and subdivided into isolated, group, and Virgo subsamples. We find a larger mean H2 mass in the Virgo galaxies compared to group galaxies, despite their lower mean Hi mass. Combining our data with complementary Hα star formation rate measurements, Virgo galaxies have a longer molecular gas depletion times compared to group galaxies, perhaps due to heating processes in the cluster environment or differences in the turbulent pressure.

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