The Role of Metallicity and H2 in Star Formation in the Galaxy

1987 ◽  
pp. 323-324
Author(s):  
N. C. Rana ◽  
D. A. Wilkinson
Keyword(s):  
Star Formation ◽  
The Galaxy

scholarly journals The Role of Metallicity and H2 in Star Formation in the Galaxy

1987 ◽  
Vol 120 ◽  
pp. 323-324
Author(s):  
N. C. Rana ◽  
D.A. Wilkinson
Keyword(s):  
Star Formation ◽  
Explicit Dependence ◽  
The Galaxy

A new law of star formation is proposed which suggests an explicit dependence on the abundance of metals and H2.

scholarly journals xGASS: the role of bulges along and across the local star-forming main sequence

2020 ◽  
Vol 493 (4) ◽  
pp. 5596-5605 ◽  
Author(s):  
Robin H W Cook ◽  
Luca Cortese ◽  
Barbara Catinella ◽  
Aaron Robotham
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Formation Rate ◽  
Stellar Mass ◽  
Local Universe ◽  
Star Forming ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Stellar Masses

ABSTRACT We use our catalogue of structural decomposition measurements for the extended GALEX Arecibo SDSS Survey (xGASS) to study the role of bulges both along and across the galaxy star-forming main sequence (SFMS). We show that the slope in the sSFR–M⋆ relation flattens by ∼0.1 dex per decade in M⋆ when re-normalizing specifice star formation rate (sSFR) by disc stellar mass instead of total stellar mass. However, recasting the sSFR–M⋆ relation into the framework of only disc-specific quantities shows that a residual trend remains against disc stellar mass with equivalent slope and comparable scatter to that of the total galaxy relation. This suggests that the residual declining slope of the SFMS is intrinsic to the disc components of galaxies. We further investigate the distribution of bulge-to-total ratios (B/T) as a function of distance from the SFMS (ΔSFRMS). At all stellar masses, the average B/T of local galaxies decreases monotonically with increasing ΔSFRMS. Contrary to previous works, we find that the upper envelope of the SFMS is not dominated by objects with a significant bulge component. This rules out a scenario in which, in the local Universe, objects with increased star formation activity are simultaneously experiencing a significant bulge growth. We suggest that much of the discrepancies between different works studying the role of bulges originate from differences in the methodology of structurally decomposing galaxies.

scholarly journals Evolution of galaxies in groups in the Coma Supercluster

2020 ◽  
Vol 497 (1) ◽  
pp. 466-481
Author(s):  
Ruchika Seth ◽  
Somak Raychaudhury
Keyword(s):  
Star Formation ◽  
Kernel Density ◽  
Local Environment ◽  
Density Estimator ◽  
Intrinsic Properties ◽  
Filament System ◽  
Cluster Group ◽  
Star Formation Activity ◽  
The Galaxy

ABSTRACT We take a close look at the galaxies in the Coma Supercluster and assess the role of the environment (in the form of cluster, group, and supercluster filament) in their evolution, in particular, examining the role of groups. We characterize the groups according to intrinsic properties such as richness and halo mass, as well as their position in the supercluster and proximity to the two rich clusters, Abell 1656 (Coma) and Abell 1367. We devise a new way of characterizing the local environment using a kernel density estimator. We find that apart from the dominant effects of the galaxy mass, the effect of the environment on galaxies is a complex combination of the overdensities on various scales, which is characterized in terms of membership of groups, and also of the position of the galaxy on filaments and their proximity to the infall regions of clusters. Whether the gas can be turned into stars depends upon the level of pre-processing, which plays a role in how star formation is enhanced in a given environment. Our results are consistent with gas accreted in the cold mode from the filaments, being made available to enhance star formation. Finally, we show that the Abell 1367 end of the supercluster is in the process of assembly at present, leading to heightened star formation activity, in contrast with the Coma-end of the filament system.

scholarly journals The irreplaceable role of ubiquitous cosmic rays in the space chemistry: from the origin of complex species in interstellar molecular clouds to the ozone depletion in the atmospheres of Earth-like planets

2020 ◽  
pp. 37-54
Author(s):  
Ararat Yeghikyan
Keyword(s):  
Star Formation ◽  
Cosmic Rays ◽  
Atmospheric Chemistry ◽  
Ozone Depletion ◽  
Molecular Clouds ◽  
Complex Species ◽  
The Galaxy ◽  
Earth Like Planets ◽  
Interstellar Molecular Clouds

A review is given of low-energy cosmic rays (1 MeV-10 GeV), which play an important role in the physics and chemistry of interstellar medium of our Galaxy. According to the generally accepted theory of star formation, cosmic rays penetrate into molecular clouds and ionize the dense gaseous medium of star formation centers besides due to a process of ambipolar diffusion they establish a star formation time scale of about 100-1000 thousand years. The source of cosmic rays in the Galaxy are supernovae remnants where diffusion acceleration at the shock front accelerates particles up to energies of 1015 eV. Being the main source of ionization in the inner regions of molecular clouds, cosmic rays play a fundamental role in the global chemistry of clouds, triggering the entire chain of ion-molecular reactions that make it possible to obtain basic molecules. The review also noted the importance of cosmic rays in atmospheric chemistry: playing a significant role in the formation of nitric oxide, especially with an increase in the flux, they cause a decrease in the concentration of ozone in the atmosphere with all climatic consequences.

scholarly journals The role of interstellar filaments in regulating the star formation efficiency and shaping the initial mass function

2015 ◽  
Vol 11 (S315) ◽  
pp. 81-84
Author(s):  
Vera Könyves ◽  
Philippe André
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Filamentary Structure ◽  
Submillimeter Wavelengths ◽  
The Galaxy ◽  
External Galaxies ◽  
Space Observatories ◽  
Formation Efficiency

AbstractRecent surveys at infrared and submillimeter wavelengths with the Spitzer and Herschel space observatories suggest that star formation in dense molecular gas is governed by essentially the same “laws” in nearby Galactic clouds and distant external galaxies. This raises the possibility of a unified picture for star formation in the Universe from individual-cloud scales to galaxy–wide scales. We summarize the star formation scenario favored by Herschel studies of the nearest molecular clouds of the Galaxy which point to the key role of the quasi-universal filamentary structure pervading the cold interstellar medium.

scholarly journals The Role of Quasars in Galaxy Formation

2009 ◽  
Vol 5 (S267) ◽  
pp. 17-25 ◽  
Author(s):  
D. Elbaz
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Positive Feedback ◽  
Local Environment ◽  
Active Role ◽  
Molecular Gas ◽  
Massive Galaxies ◽  
Radio Jets ◽  
The Galaxy

AbstractWe discuss evidence that quasars, and more generally radio jets, may have played an active role in the formation stage of galaxies by inducing star formation, i.e., through positive feedback. This mechanism first proposed in the 1970s has been considered as anecdotal until now, contrary to the opposite effect that is generally put forward, i.e., the quenching of star formation in massive galaxies to explain the galaxy bimodality, downsizing, and the universal black hole mass over bulge stellar mass ratio. This suggestion is based on the recent discovery of an ultra-luminous infrared galaxy, i.e., an extreme starburst, that appears to be triggered by a radio jet from the QSO HE 0450-2958 at z = 0.2863, together with the finding in several systems of a positional offset between molecular gas and quasars, which may be explained by the positive feedback effect of radio jets on their local environment.

scholarly journals Environmental effects in galaxies – searching for massive stars

1999 ◽  
Vol 193 ◽  
pp. 739-740
Author(s):  
Duíla F. de Mello ◽  
Marcio A.G. Maia ◽  
Daniel Schaerer ◽  
Claus Leitherer
Keyword(s):  
Star Formation ◽  
Environmental Effects ◽  
Massive Star ◽  
Massive Stars ◽  
Starburst Galaxies ◽  
High Density ◽  
Massive Star Formation ◽  
The Galaxy ◽  
Galaxy Population

In order to study the influence of the environment in galaxies we have selected a sample from the catalog by Maia et al. (1994) which contains objects in low and high density areas of the Southern sky. These samples have been observed with the Brazilian-ESO 1.52m telescope and long-slit spectra are being analyzed. With our database we will be able to investigate the role of the environment in the galaxy population. We will be able to search for WR features and massive stars. It is our goal to compare the general properties of these galaxies with typical starburst galaxies which are dominated by episodes of massive star formation.

scholarly journals A phenomenological approach to the evolution of galaxies

2012 ◽  
Vol 8 (S295) ◽  
pp. 141-150
Author(s):  
Simon J. Lilly ◽  
Yingjie Peng ◽  
Marcella Carollo ◽  
Alvio Renzini
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Statistical Data ◽  
Phenomenological Approach ◽  
Star Forming ◽  
Continuity Equations ◽  
The Galaxy ◽  
Star Formation In Galaxies ◽  
Galaxy Population

AbstractIncreasingly good statistical data on the galaxy population at high and low redshift enable the development of new phenomenological approaches to galaxy evolution based on application of the simplest continuity equations. This has given new insights into the different ways in which star-formation in galaxies is quenched, the role of merging in the population, and in to the control of star-formation in star-forming galaxies and the links with chemical evolution. The continuity approach provides a self-consistent view of the evolving population and exposes linkages between different aspects of galaxy evolution.

scholarly journals Star Formation in the Central Molecular Zone of the Milky Way

2010 ◽  
Vol 6 (S270) ◽  
pp. 359-362
Author(s):  
Sungsoo S. Kim ◽  
Takayuki R. Saitoh ◽  
Myoungwon Jeon ◽  
David Merritt ◽  
Donald F. Figer ◽  
...  
Keyword(s):  
Star Formation ◽  
Galactic Center ◽  
Galactic Disk ◽  
Formation Rate ◽  
Infrared Observations ◽  
Recent Estimate ◽  
The Galaxy ◽  
Self Gravity ◽  
Supernova Feedback

AbstractGas materials in the inner Galactic disk continuously migrate toward the Galactic center (GC) due to interactions with the bar potential, magnetic fields, stars, and other gaseous materials. Those in forms of molecules appear to accumulate around 200 pc from the center (the central molecular zone, CMZ) to form stars there and further inside. The bar potential in the GC is thought to be responsible for such accumulation of molecules and subsequent star formation, which is believed to have been continuous throughout the lifetime of the Galaxy. We present 3-D hydrodynamic simulations of the CMZ that consider self-gravity, radiative cooling, and supernova feedback, and discuss the efficiency and role of the star formation in that region. We find that the gas accumulated in the CMZ by a bar potential of the inner bulge effectively turns into stars, supporting the idea that the stellar cusp inside the central 200 pc is a result of the sustained star formation in the CMZ. The obtained star formation rate in the CMZ, 0.03–0.1 M⊙, is consistent with the recent estimate based on the mid-infrared observations by Yusef-Zadeh et al. (2009).

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