VLA-ANGST: Star Formation History and ISM Feedback in Nearby Galaxies

2008 ◽  
pp. 321-322
Author(s):  
Jurgen Ott ◽  
Evan Skillman ◽  
Julianne Dalcanton ◽  
Fabian Walter ◽  
Andrew West ◽  
...  
Keyword(s):  
Star Formation ◽  
Star Formation History ◽  
Formation History ◽  
Nearby Galaxies

Recovering the star formation history of galaxies through spectral fitting: Current challenges

2019 ◽  
Vol 15 (S359) ◽  
pp. 386-390
Author(s):  
Lucimara P. Martins
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Stellar Spectra ◽  
Spectral Fitting ◽  
Formation History ◽  
History Of ◽  
Nearby Galaxies ◽  
Extract Information

AbstractWith the exception of some nearby galaxies, we cannot resolve stars individually. To recover the galaxies star formation history (SFH), the challenge is to extract information from their integrated spectrum. A widely used tool is the full spectral fitting technique. This consists of combining simple stellar populations (SSPs) of different ages and metallicities to match the integrated spectrum. This technique works well for optical spectra, for metallicities near solar and chemical histories not much different from our Galaxy. For everything else there is room for improvement. With telescopes being able to explore further and further away, and beyond the optical, the improvement of this type of tool is crucial. SSPs use as ingredients isochrones, an initial mass function, and a library of stellar spectra. My focus are the stellar libraries, key ingredient for SSPs. Here I talk about the latest developments of stellar libraries, how they influence the SSPs and how to improve them.

scholarly journals The star-formation history of the Universe from the stellar populations of nearby galaxies

Nature ◽  
2004 ◽  
Vol 428 (6983) ◽  
pp. 625-627 ◽  
Author(s):  
Alan Heavens ◽  
Benjamin Panter ◽  
Raul Jimenez ◽  
James Dunlop
Keyword(s):  
Star Formation ◽  
Stellar Populations ◽  
Star Formation History ◽  
Formation History ◽  
History Of ◽  
Nearby Galaxies ◽  
The Universe

scholarly journals Stellar populations in the centers of nearby galaxies

2011 ◽  
Vol 7 (S284) ◽  
pp. 234-236
Author(s):  
Jean Michel Gomes ◽  
Mercedes E. Filho ◽  
Luis C. Ho
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Spectral Synthesis ◽  
Spectral Energy Distribution ◽  
Optical Emission ◽  
Stellar Populations ◽  
Star Formation History ◽  
Spectral Energy ◽  
Formation History ◽  
Nearby Galaxies

AbstractThe great amount of data observed in recent years coupled with modelling using evolutionary synthesis codes (BPASS, COELHO, GALAXEV, GALEV, MILES, PÉGASE, etc. . .) to compute Single Stellar Populations (SSPs) and the availability of fast and ingenious spectral synthesis codes such as starlight, ULySS and VESPA, have significantly shed light on our knowledge about the formation and evolution of galaxies. However, there are still open issues concerning the stellar populations in nearby galaxies, particularly those harbouring Active Galactic Nuclei (AGN): can stellar populations mimic nuclear activity, leading to a misclassification based on optical emission line ratios (Stasińska et al. 2008)? We have applied the starlight code (Cid Fernandes et al. 2005) to a well studied sample of nearby galaxies' nuclear spectra (r < ~ 200 pc), observed with the Hale 5 m telescope at Palomar Observatory in two different regions: ~ 4230-5110 Å and ~ 6210-6860 Å (Ho et al. 1995), with spectral resolutions of approximately 4 Å, and 2.5 Å. The aim is to properly derive the star-formation history (SFH), mean stellar age and metallicity and total stellar mass. Our results show that the star-formation history of Seyfert galaxies are very heterogeneous, i.e. these are composed of young, intermediate and old stellar populations, while the SFH of Low-Ionization Nuclear Emission-Line Regions (LINERs) are basically composed of old stellar populations. The absence of young stars in LINERs indicates that these are not responsible for the observed low-ionization emission lines. Furthermore, although a significant fraction of AGN spectra require a featureless continuum in their Spectral Energy Distribution (SED) modelling, this is not an indicative of the presence of an AGN, instead the continuum may simulate the presence of young stellar populations. The main objective of this research is to complement the study of spectroscopic parameters from 486 galaxies analyzed by Ho et al. (1995) that are public available in the VizieR catalog (Ho et al. 1997, 2009) and provide information about their stellar population content by means of the starlight. The base of Simple Stellar Populations used here was taken from Bruzual & Charlot (2003) and spans 25 ages (from 1 Myr to 18 Gyr) and 6 metallicities (Z = 0.005, 0.02, 0.2, 0.4, 1 & 2.5 Z⊙).

The Star Formation History of the Local Group Dwarf Galaxy Leo I

1999 ◽  
Vol 118 (5) ◽  
pp. 2245-2261 ◽  
Author(s):  
Carme Gallart ◽  
Wendy L. Freedman ◽  
Antonio Aparicio ◽  
Giampaolo Bertelli ◽  
Cesare Chiosi
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxy ◽  
Star Formation History ◽  
Formation History ◽  
History Of

scholarly journals Is there enough star formation in simulated protoclusters?

2020 ◽  
Vol 501 (2) ◽  
pp. 1803-1822
Author(s):  
Seunghwan Lim ◽  
Douglas Scott ◽  
Arif Babul ◽  
David J Barnes ◽  
Scott T Kay ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Star Formation History ◽  
Test Case ◽  
Numerical Resolution ◽  
Formation History ◽  
Order Of Magnitude ◽  
History Of ◽  
Hydrodynamical Simulations ◽  
Formation Efficiency

ABSTRACT As progenitors of the most massive objects, protoclusters are key to tracing the evolution and star formation history of the Universe, and are responsible for ${\gtrsim }\, 20$ per cent of the cosmic star formation at $z\, {\gt }\, 2$. Using a combination of state-of-the-art hydrodynamical simulations and empirical models, we show that current galaxy formation models do not produce enough star formation in protoclusters to match observations. We find that the star formation rates (SFRs) predicted from the models are an order of magnitude lower than what is seen in observations, despite the relatively good agreement found for their mass-accretion histories, specifically that they lie on an evolutionary path to become Coma-like clusters at $z\, {\simeq }\, 0$. Using a well-studied protocluster core at $z\, {=}\, 4.3$ as a test case, we find that star formation efficiency of protocluster galaxies is higher than predicted by the models. We show that a large part of the discrepancy can be attributed to a dependence of SFR on the numerical resolution of the simulations, with a roughly factor of 3 drop in SFR when the spatial resolution decreases by a factor of 4. We also present predictions up to $z\, {\simeq }\, 7$. Compared to lower redshifts, we find that centrals (the most massive member galaxies) are more distinct from the other galaxies, while protocluster galaxies are less distinct from field galaxies. All these results suggest that, as a rare and extreme population at high z, protoclusters can help constrain galaxy formation models tuned to match the average population at $z\, {\simeq }\, 0$.

scholarly journals How robustly can we constrain the low-mass end of the z ∼ 6−7 stellar mass function? The limits of lensing models and stellar population assumptions in the Hubble Frontier Fields

2020 ◽  
Vol 501 (2) ◽  
pp. 1568-1590
Author(s):  
Lukas J Furtak ◽  
Hakim Atek ◽  
Matthew D Lehnert ◽  
Jacopo Chevallard ◽  
Stéphane Charlot
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Stellar Mass ◽  
Star Formation History ◽  
Space Telescope ◽  
Formation History ◽  
Low Mass ◽  
Stellar Masses ◽  
Dust Attenuation ◽  
The Impact

ABSTRACT We present new measurements of the very low mass end of the galaxy stellar mass function (GSMF) at z ∼ 6−7 computed from a rest-frame ultraviolet selected sample of dropout galaxies. These galaxies lie behind the six Hubble Frontier Field clusters and are all gravitationally magnified. Using deep Spitzer/IRAC and Hubble Space Telescope imaging, we derive stellar masses by fitting galaxy spectral energy distributions and explore the impact of different model assumptions and parameter degeneracies on the resulting GSMF. Our sample probes stellar masses down to $M_{\star }\gt 10^{6}\, \text{M}_{\odot}$ and we find the z ∼ 6−7 GSMF to be best parametrized by a modified Schechter function that allows for a turnover at very low masses. Using a Monte Carlo Markov chain analysis of the GSMF, including accurate treatment of lensing uncertainties, we obtain a relatively steep low-mass end slope $\alpha \simeq -1.96_{-0.08}^{+0.09}$ and a turnover at $\log (M_T/\text{M}_{\odot})\simeq 7.10_{-0.56}^{+0.17}$ with a curvature of $\beta \simeq 1.00_{-0.73}^{+0.87}$ for our minimum assumption model with constant star formation history (SFH) and low dust attenuation, AV ≤ 0.2. We find that the z ∼ 6−7 GSMF, in particular its very low mass end, is significantly affected by the assumed functional form of the star formation history and the degeneracy between stellar mass and dust attenuation. For example, the low-mass end slope ranges from $\alpha \simeq -1.82_{-0.07}^{+0.08}$ for an exponentially rising SFH to $\alpha \simeq -2.34_{-0.10}^{+0.11}$ when allowing AV of up to 3.25. Future observations at longer wavelengths and higher angular resolution with the James Webb Space Telescope are required to break these degeneracies and to robustly constrain the stellar mass of galaxies on the extreme low-mass end of the GSMF.

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