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 Binary stars on the galaxy SFH

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
F. Zhang ◽  
L. Li ◽  
Z. Han
Keyword(s):  
Star Formation ◽  
Binary Stars ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Formation History ◽  
Population Synthesis ◽  
Feedback Process ◽  
Formation History ◽  
The Galaxy ◽  
Degeneracy Problem

AbstractUsing the Yunnan-II evolutionary population synthesis models comprising binary stars, we find that the inclusion of binary stars can raise the derived stellar metallicity Z* and/or age t (degeneracy problem), raise the stellar mass M*, lower the gaseous metallicity Zgas and star formation rate (SFR) of galaxies. This means that a few stars form recently in galaxies, while more stars form during the entire evolution process when considering binary stars. If the degeneracy between t and Z* can be broken, its effect on the feedback process and star formation history can be determined.

scholarly journals The star formation history of galaxies in 3D: CALIFA perspective

2014 ◽  
Vol 10 (S309) ◽  
pp. 99-104
Author(s):  
R. M. González Delgado ◽  
R. Cid Fernandes ◽  
R. García-Benito ◽  
E. Pérez ◽  
A. L. de Amorim ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Density ◽  
Spectral Synthesis ◽  
Stellar Mass ◽  
Star Formation History ◽  
Chemical Enrichment ◽  
Radial Profiles ◽  
Formation History ◽  
The Galaxy ◽  
History Of

AbstractWe resolve spatially the star formation history of 300 nearby galaxies from the CALIFA integral field survey to investigate: a) the radial structure and gradients of the present stellar populations properties as a function of the Hubble type; and b) the role that plays the galaxy stellar mass and stellar mass surface density in governing the star formation history and metallicity enrichment of spheroids and the disks of galaxies. We apply the fossil record method based on spectral synthesis techniques to recover spatially and temporally resolved maps of stellar population properties of spheroids and spirals with galaxy mass from 109 to 7×1011 M⊙. The individual radial profiles of the stellar mass surface density (μ⋆), stellar extinction (AV), luminosity weighted ages (〈logage〉L), and mass weighted metallicity (〈log Z/Z⊙〉M) are stacked in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc and Sd). All these properties show negative gradients as a sight of the inside-out growth of massive galaxies. However, the gradients depend on the Hubble type in different ways. For the same galaxy mass, E and S0 galaxies show the largest inner gradients in μ⋆; and Andromeda-like galaxies (Sb with log M⋆ (M⊙) ∼ 11) show the largest inner age and metallicity gradients. In average, spiral galaxies have a stellar metallicity gradient ∼ −0.1 dex per half-light radius, in agreement with the value estimated for the ionized gas oxygen abundance gradient by CALIFA. A global (M⋆-driven) and local (μ⋆-driven) stellar metallicity relation are derived. We find that in disks, the stellar mass surface density regulates the stellar metallicity; in spheroids, the galaxy stellar mass dominates the physics of star formation and chemical enrichment.

scholarly journals Cosmic Star Formation from the Milky Way and its Satellites

1999 ◽  
Vol 190 ◽  
pp. 8-14
Author(s):  
F.D.A. Hartwick
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Formation History ◽  
Evolutionary Models ◽  
Disk Mass ◽  
Formation History ◽  
History Of ◽  
The Universe

We use observations and evolutionary models of local objects to interpret a recent determination of the star-formation history of the universe. By fitting the global star-formation rate, the model predicts the ratio of spheroid to disk mass of ~1, an intergalactic medium (IGM) whose mass is ~2.3 times the mass in stars, and whose metallicity is ~0.1 Z⊙.

Reconstructing the star formation history of the Solar neighbourhood with Gaia

2017 ◽  
Vol 13 (S334) ◽  
pp. 158-161
Author(s):  
Edouard J. Bernard
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Formation History ◽  
Solar Neighbourhood ◽  
The Past ◽  
Formation History ◽  
Magnitude Diagram ◽  
History Of

AbstractTaking advantage of the Gaia DR1, we combined TGAS parallaxes with the Tycho-2 and APASS photometry to calculate the star formation history (SFH) of the solar neighbourhood within 250 pc using the colour-magnitude diagram fitting technique. Our dynamically-evolved SFH is in excellent agreement with that calculated from the Hipparcos catalogue within 80 pc of the Sun, showing an enhanced star formation rate (SFR) in the past ~4 Gyr. We then correct the SFR for the disc thickening with age to obtain a SFR that is representative of the whole solar cylinder, and show that even with an extreme correction our results are not consistent with an exponentially decreasing SFR as found by recent studies. Finally, we discuss how this technique can be applied out to ~5 kpc thanks to the next Gaia data releases, which will allow us to quantify the SFH of the thin disc, thick disc and halo in situ.

scholarly journals Beryllium abundances and the formation of the halo and the thick disk

2009 ◽  
Vol 5 (S268) ◽  
pp. 483-488
Author(s):  
Rodolfo Smiljanic ◽  
L. Pasquini ◽  
P. Bonifacio ◽  
D. Galli ◽  
B. Barbuy ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Thick Disk ◽  
Star Formation History ◽  
Halo Stars ◽  
Formation History ◽  
The Galaxy ◽  
History Of ◽  
Early Galaxy

AbstractThe single stable isotope of beryllium is a pure product of cosmic-ray spallation in the ISM. Assuming that the cosmic-rays are globally transported across the Galaxy, the beryllium production should be a widespread process and its abundance should be roughly homogeneous in the early-Galaxy at a given time. Thus, it could be useful as a tracer of time. In an investigation of the use of Be as a cosmochronometer and of its evolution in the Galaxy, we found evidence that in a log(Be/H) vs. [α/Fe] diagram the halo stars separate into two components. One is consistent with predictions of evolutionary models while the other is chemically indistinguishable from the thick-disk stars. This is interpreted as a difference in the star formation history of the two components and suggests that the local halo is not a single uniform population where a clear age-metallicity relation can be defined. We also found evidence that the star formation rate was lower in the outer regions of the thick disk, pointing towards an inside-out formation.

scholarly journals Two distinct halo populations in the solar neighborhood: evidence from stellar abundance of beryllium

2013 ◽  
Vol 9 (S298) ◽  
pp. 83-85
Author(s):  
Kefeng Tan ◽  
Gang Zhao
Keyword(s):  
Star Formation ◽  
Galactic Halo ◽  
Formation Rate ◽  
Solar Neighborhood ◽  
Elemental Abundance ◽  
Star Formation History ◽  
Dwarf Stars ◽  
Formation History ◽  
The Galaxy ◽  
History Of

AbstractIt is now generally believed that the Galaxy was formed through hierarchical merging, which means that different components of the Galaxy may have experienced different chemical evolution histories. Since alpha elements are mainly produced by core collapse supernovae, they are closely associated with the star formation history of the Galaxy. In this regard, Galactic components with different alpha elemental abundance patterns may show different behaviors in beryllium abundances since the production of beryllium is correlated with the cosmic rays and thus the supernovae. A recent study by Nissen & Schuster (2010) has revealed the existence of two distinct halo populations in the solar neighborhood based on the alpha elemental abundances and kinematics of 94 dwarf stars. We determined beryllium abundances for some of these stars and find systematic differences in beryllium abundances between these two halo populations. Our results consolidate the conclusion of two distinct halo populations in the solar neighborhood. Our results also show that beryllium abundance is a very good indicator of star formation rate, and could be used to trace the substructures of the Galactic halo.

scholarly journals The IMF and star-formation history of the ionizing cluster of 30 Doradus

1999 ◽  
Vol 193 ◽  
pp. 495-496
Author(s):  
Fernando J. Selman ◽  
Jorge Melnick ◽  
Guillermo L. Bosch ◽  
Roberto J. Terlevich
Keyword(s):  
Star Formation ◽  
Power Law ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Formation History ◽  
Formation History ◽  
History Of ◽  
Single Power ◽  
30 Doradus ◽  
The Imf

A new method is used to determine masses, ages, and reddening for the stars of the starburst cluster NGC 2070 in 30 Doradus. The data are consistent with a star-formation rate which increases exponentially with a characteristic rise time of 1.7 Myr, independent of mass, starting 7 Myr ago. The IMF is consistent with a single power law IMF with Salpeter slope over the whole 3 M⊙ < M < 120 M⊙ range investigated, with evidence for flattening for the innermost radial bin.

scholarly journals The Star Formation History of the GRB 050730 Host Galaxy

2008 ◽  
Vol 4 (S255) ◽  
pp. 217-223
Author(s):  
Francesco Calura
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Chemical Elements ◽  
Formation Rate ◽  
Star Formation History ◽  
Host Galaxy ◽  
Lyman Alpha ◽  
Formation History ◽  
History Of

AbstractThe long GRB 050730 observed at redshiftz~ 4 allowed the determination of the elemental abundances for a set of different chemical elements. We use detailed chemical evolution models taking into account also dust production to constrain the star formation history of the host galaxy of this long GRB. For the host galaxy of GRB 050730, we derive also some dust-related quantities and the specific star formation rate, namely the star formation rate per unit stellar mass. Finally, we compare the properties of the GRB host galaxy with those of Quasar Damped Lyman Alpha absorbers.

scholarly journals White dwarfs as advanced physics laboratories. The axion case

2019 ◽  
Vol 15 (S357) ◽  
pp. 138-153
Author(s):  
Jordi Isern
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
White Dwarfs ◽  
Luminosity Function ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Formation History ◽  
Formation History ◽  
The Galaxy ◽  
Physics Laboratories

AbstractThe shape of the luminosity function of white dwarfs (WDLF) is sensitive to the characteristic cooling time and, therefore, it can be used to test the existence of additional sources or sinks of energy such as those predicted by alternative physical theories. However, because of the degeneracy between the physical properties of white dwarfs and the properties of the Galaxy, the star formation history (SFH) and the IMF, it is almost always possible to explain any anomaly as an artifact introduced by the star formation rate. To circumvent this problem there are at least two possibilities, the analysis of the WDLF in populations with different stories, like disc and halo, and the search of effects not correlated with the SFH. These procedures are illustrated with the case of axions.

scholarly journals Chemo-dynamical simulations of galaxies

2009 ◽  
Vol 5 (S265) ◽  
pp. 336-341
Author(s):  
Chiaki Kobayashi
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Formation History ◽  
Chemical Abundances ◽  
Chemical Enrichment ◽  
Formation History ◽  
Dynamical Simulations ◽  
Formation And Evolution ◽  
Supernova Feedback

AbstractWe simulate the formation and evolution of galaxies with a self-consistent 3D hydrodynamical model including star formation, supernova feedback, and chemical enrichment. Hypernova feedback plays an essential role not only in solving the [Zn/Fe] problem, but also reproducing the cosmic star formation rate history and the mass-metallicity relations. In the Milky-Way type galaxy, the star formation history, and thus the kinematics and chemical abundances are different in bulge, disk, and thick disk.

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