scholarly journals Dispersal of massive star products and consequences for galactic chemical evolution

2003 ◽  
Vol 212 ◽  
pp. 620-629
Author(s):  
M. S. Oey
Keyword(s):  
Chemical Evolution ◽  
Massive Star ◽  
Milky Way ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Products ◽  
Galactic Chemical Evolution ◽  
Mixing Processes ◽  
Nearby Galaxies ◽  
Metallicity Distribution

The processes that disperse the products of massive stars from their birth sites play a fundamental role in determining the observed abundances. I discuss parameterizations for element dispersal and their roles in chemical evolution, with an emphasis on understanding present-day dispersion and homogeneity in metallicity. Turbulence dominates mixing processes, with characteristic timescales of order 108 yr, implying significant dilution of metals into the ISM. This permits a rough estimate of the metallicity distribution function of enrichment events. Many systems, including the Milky Way and nearby galaxies, show metallicity dispersions that as yet appear consistent with pure inhomogeneous evolution. There are also systems like I Zw 18 that show strong homogenization, perhaps tied to small galaxy size, high star formation rate, and/or superwinds.

scholarly journals Interactions and star formation

2015 ◽  
Vol 11 (S315) ◽  
pp. 236-239
Author(s):  
Johan H. Knapen ◽  
Mauricio Cisternas ◽  
Miguel Querejeta
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Morphological Type ◽  
Stellar Mass ◽  
Interacting Galaxies ◽  
The Galaxy ◽  
Nearby Galaxies ◽  
Ir Emission

AbstractWe investigate the influence of interactions on the star formation by studying a sample of almost 1500 of the nearest galaxies, all within a distance of ~45 Mpc. We define the massive star formation rate (SFR), as measured from far-IR emission, and the specific star formation rate (SSFR), which is the former quantity normalized by the stellar mass of the galaxy, and explore their distribution with morphological type and with stellar mass. We then calculate the relative enhancement of these quantities for each galaxy by normalizing them by the median SFR and SSFR values of individual control populations of similar non-interacting galaxies. We find that both SFR and SSFR are enhanced in interacting galaxies, and more so as the degree of interaction is higher. The increase is, however, moderate, reaching a maximum of a factor of 1.9 for the highest degree of interaction (mergers). The SFR and SSFR are enhanced statistically in the population, but in most individual interacting galaxies they are not enhanced at all. We discuss how those galaxies with the largest SFR and/or SSFR enhancement can be defined as starbursts. We argue that this study, based on a representative sample of nearby galaxies, should be used to place constraints on studies based on samples of galaxies at larger distances.

scholarly journals The Red MSX Source Survey - Massive Star Formation in the Milky Way

2009 ◽  
Vol 5 (H15) ◽  
pp. 801-801
Author(s):  
Stuart Lumsden ◽  
Melvin Hoare ◽  
Ben Davis ◽  
Keyword(s):  
Star Formation ◽  
Accretion Disks ◽  
Massive Star ◽  
Milky Way ◽  
Star Formation Rate ◽  
Massive Stars ◽  
Formation Rate ◽  
Massive Star Formation

AbstractWe present the results of a Galaxy-wide survey for young massive stars still in the process of formation. Our data are consistent with a model in which the stars form through accretion disks with the overall Galactic star formation rate being 3 M⊙ per year.

scholarly journals Baryonic inflow and outflow histories in disk galaxies as revealed from observations of distant star-forming galaxies

2015 ◽  
Vol 11 (S317) ◽  
pp. 356-357
Author(s):  
Daisuke Toyouchi ◽  
Masashi Chiba
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Milky Way ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Chemical Abundance ◽  
Star Forming ◽  
Distant Star ◽  
Fundamental Information ◽  
Outflow Rate

AbstractGas inflow and outflow are the most important processes, which determine the structural and chemical evolution of a disk galaxy like the Milky Way. In order to get new insights into these baryonic processes in Milky Way like galaxies (MWLGs), we consider the data of distant star-forming galaxies and investigate the evolution of the radial density profile of their stellar components and the associated total amount of gaseous inflow and outflow. For this purpose, we analyze the redshift evolution of their stellar mass distribution, combined with the scaling relations between the mass of baryonic components, star formation rate and chemical abundance for both high- and low-z star-forming galaxies. As a result, we find the new relations between star formation rate and inflow/outflow rate as deduced from these distant galaxies, which will provide fundamental information for understanding the structural and chemical evolution of MWLGs.

scholarly journals The systematically varying stellar IMF

2019 ◽  
Vol 14 (S351) ◽  
pp. 117-121 ◽  
Author(s):  
Pavel Kroupa
Keyword(s):  
Globular Clusters ◽  
Massive Star ◽  
Milky Way ◽  
Dwarf Galaxies ◽  
Star Formation Rate ◽  
High Redshift ◽  
Formation Rate ◽  
Low Mass Stars ◽  
Dynamical Mass ◽  
Low Mass

AbstractSome ultra-compact dwarf galaxies have large dynamical mass to light (M / L) ratios and also appear to contain an overabundance of LMXB sources, and some Milky Way globular clusters have a low concentration and appear to have a deficit of low-mass stars. These observations can be explained if the stellar IMF becomes increasingly top-heavy with decreasing metallicity and increasing gas density of the forming object. The thus constrained stellar IMF then accounts for the observed trend of metallicity and M / L ratio found amongst M31 globular star clusters. It also accounts for the overall shift of the observationally deduced galaxy-wide IMF from top-light to top-heavy with increasing star formation rate amongst galaxies. If the IMF varies similarly to deduced here, then extremely young very massive star-burst clusters observed at a high redshift would appear quasar-like (Jerabkova et al. 2017).

scholarly journals The dense galactic environments of the Milky Way

2018 ◽  
Vol 14 (S345) ◽  
pp. 34-38
Author(s):  
Quang Nguyen-Luong ◽  
Neal Evans ◽  
Kee-Tae Kim ◽  
Hyunwoo Kang ◽  
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Massive Star ◽  
Milky Way ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Dense Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Rate Relation

AbstractStar formation takes place in the dense gas phase, and therefore a simple dense gas and star formation rate relation has been proposed. With the advent of multi-beam receivers, new observations show that the deviation from linear relations is possible. In addition, different dense gas tracers might also change significantly the measurement of dense gas mass and subsequently the relation between star formation rate and dense gas mass. We report the preliminary results the DEnse GAs in MAssive star-forming regions in the Milky Way (DEGAMA) survey that observed the dense gas toward a suite of well-characterized massive star-forming regions in the Milky Way. Using the resulting maps of HCO+ 1–0, HCN 1–0, CS 2–1, we discuss the current understanding of the dense gas phase where star formation takes place.

scholarly journals The Metallicity Distribution of Late Type Dwarfs

1998 ◽  
Vol 11 (1) ◽  
pp. 571-571
Author(s):  
M. Haywood ◽  
J. Palasi ◽  
A. Gómez ◽  
L. Meillon Dasgal
Keyword(s):  
Star Formation Rate ◽  
Formation Rate ◽  
Angular Separation ◽  
Stellar Populations ◽  
Late Type ◽  
Limited Sample ◽  
Hipparcos Catalogue ◽  
Galactic Stellar Populations ◽  
Metallicity Distribution ◽  
Hr Diagram

The Hipparcos catalogue provides an accurate and extensive sampling of the solar neighbourhood HR diagram. The morphology of this diagram depends on selection criteria of the catalogue such as the limiting magnitude, angular separation and on the characteristics of the stellar populations near the sun (space density, metallicity, star formation rate, etc). Since the Hipparcos data are so accurate, one needs to model precisely the different selection bias and, at the same time, parametrize models of the galactic stellar populations with sufficient flexibility that as much information as possible can be grasped from the catalogue. Comparisons between our model and the Hipparcos catalogue will be presented elsewhere. Since the quantity of information contained in the Hipparcoscatalogue is so important, models ought to be complex, and external contraints, obtained prior to any general comparison with the model, are welcome. A major factor that influences the distribution of the stars in the HR diagram is the metallicity. For the late type stars, the metallicity distribution can be best studied by re-analysing a volume-limited sample of stars from the catalogue.

scholarly journals Testing galaxy formation simulations with damped Lyman-α abundance and metallicity evolution

2020 ◽  
Vol 492 (2) ◽  
pp. 2835-2846 ◽  
Author(s):  
Sultan Hassan ◽  
Kristian Finlator ◽  
Romeel Davé ◽  
Christopher W Churchill ◽  
J Xavier Prochaska
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Star Formation Rate ◽  
Initial Conditions ◽  
Mass Density ◽  
Formation Rate ◽  
Thomson Scattering ◽  
Stellar Mass ◽  
Rate Functions ◽  
Metallicity Distribution

ABSTRACT We examine the properties of damped Lyman-α absorbers (DLAs) emerging from a single set of cosmological initial conditions in two state-of-the-art cosmological hydrodynamic simulations: simba and technicolor dawn. The former includes star formation and black hole feedback treatments that yield a good match with low-redshift galaxy properties, while the latter uses multifrequency radiative transfer to model an inhomogeneous ultraviolet background (UVB) self-consistently and is calibrated to match the Thomson scattering optical depth, UVB amplitude, and Ly α forest mean transmission at z > 5. Both simulations are in reasonable agreement with the measured stellar mass and star formation rate functions at z ≥ 3, and both reproduce the observed neutral hydrogen cosmological mass density, $\Omega _{\rm H\, \small{I}}(z)$. However, the DLA abundance and metallicity distribution are sensitive to the galactic outflows’ feedback and the UVB amplitude. Adopting a strong UVB and/or slow outflows underproduces the observed DLA abundance, but yields broad agreement with the observed DLA metallicity distribution. By contrast, faster outflows eject metals to larger distances, yielding more metal-rich DLAs whose observational selection may be more sensitive to dust bias. The DLA metallicity distribution in models adopting an H2-regulated star formation recipe includes a tail extending to [M/H] ≪ −3, lower than any DLA observed to date, owing to curtailed star formation in low-metallicity galaxies. Our results show that DLA observations play an important role in constraining key physical ingredients in galaxy formation models, complementing traditional ensemble statistics such as the stellar mass and star formation rate functions.

scholarly journals Evolution of the star formation efficiency in galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 341-341
Author(s):  
Jonathan Braine
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Conversion Factor ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Molecular Gas ◽  
Present Evidence ◽  
Ngc 6822 ◽  
Physical And Chemical ◽  
Formation Efficiency

AbstractThe physical and chemical evolution of galaxies is intimately linked to star formation, We present evidence that molecular gas (H2) is transformed into stars more quickly in smaller and/or subsolar metallicity galaxies than in large spirals – which we consider to be equivalent to a star formation efficiency (SFE). In particular, we show that this is not due to uncertainties in the N(H2)/Ico conversion factor. Several possible reasons for the high SFE in galaxies like the nearby M33 or NGC 6822 are proposed which, separately or together, are the likely cause of the high SFE in this environment. We then try to estimate how much this could contribute to the increase in cosmic star formation rate density from z = 0 to z = 1.

scholarly journals The Chemical Evolution of Light Elements in Our Galaxy

2002 ◽  
Vol 187 ◽  
pp. 47-56
Author(s):  
N. Prantzos
Keyword(s):  
Chemical Evolution ◽  
Star Formation Rate ◽  
Past History ◽  
Formation Rate ◽  
Solar Neighborhood ◽  
Gas Content ◽  
Disk Galaxies ◽  
The Past ◽  
History Of ◽  
Metal Abundances

Progress in the theory of galactic chemical evolution has been very slow and it is only in the solar neighborhood that observations constrain seriously the parameters of the various models. The history revealed on the basis of these data allows only for a small depletion of deuterium (D), less than a factor of 3 from its pregalactic value (Sec. 2.1). The observational data for the rest of the Milky Way disk are much less constraining for the models. They suggest, however, that a much larger astration (and, hence, D depletion) has taken place in the inner Galaxy; the resulting D gradient, measurable by the future FUSE-LYMAN mission, should provide invaluable information as to the past history of the disk (Sec. 2.2). Also, assuming that our Galaxy is a typical spiral, one can calculate the properties of disk galaxies as a function of redshift (in the framework of a given cosmological model) and compare to the observed properties of the extragalactic universe: global star formation rate, gas content and metal abundances in gas clouds. It turns out that D can be considerably depleted in galaxy disks, but only at low redshifts (Sec. 2.3).

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