scholarly journals Chemical Evolution in Hierarchical Clustering Scenarios

2004 ◽  
Vol 217 ◽  
pp. 258-263
Author(s):  
Patricia B. Tissera ◽  
Cecilia Scannapieco
Keyword(s):  
Star Formation ◽  
Energy Distribution ◽  
Chemical Evolution ◽  
Star Formation Rate ◽  
Spectral Synthesis ◽  
Formation Rate ◽  
First Results ◽  
History Of ◽  
Chemical History ◽  
The Impact

We present first results of an implementation of chemical evolution in a cosmological hydrodynamical code, focusing the analysis on the effects of cooling baryons according to their metallicity. We found that simulations with primordial cooling can underestimate the star formation rate from z < 3 and by up to ≈ 20%. We constructed simulated spectra by combining the star formation and chemical history of galactic systems with spectral synthesis models and assess the impact of chemical evolution on the energy distribution.

scholarly journals Emission Line Galaxies at 1 < z < 1.5

1999 ◽  
Vol 186 ◽  
pp. 467-470
Author(s):  
K. Glazebrook ◽  
R.G. Abraham ◽  
C.A. Blake
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Emission Lines ◽  
Redshift Surveys ◽  
First Results ◽  
History Of ◽  
Emission Line Galaxies ◽  
Hubble Deep Field

In this paper we wish to introduce the first results on two new projects aimed at detecting emission lines in galaxies at z > 1. There are two primary motivations for doing this: Firstly to try and measure the cosmic star-formation rate at these redshifts. The combination of z < 1 redshift surveys and the discovery of the z ~ 3 Hubble Deep Field ultraviolet dropout objects has led to a ‘first draft’ history of the cosmic SFR (Fig. 1). These results are based on UV continuum fluxes, it is highly desirably to confirm these studies with line diagnostics and extend the work to the redshift of the inferred peak (z ~ 1.5).

The impact of star formation sampling effects on the spectra of lensed z > 6 galaxies detectable with JWST

2019 ◽  
Vol 492 (2) ◽  
pp. 1706-1712
Author(s):  
Anton Vikaeus ◽  
Erik Zackrisson ◽  
Christian Binggeli
Keyword(s):  
Star Formation ◽  
Spectral Synthesis ◽  
High Redshift ◽  
Formation Rate ◽  
Mass Function ◽  
Spectroscopic Studies ◽  
Initial Mass Function ◽  
James Webb Space Telescope ◽  
Population Iii Stars ◽  
The Impact

ABSTRACT The upcoming James Webb Space Telescope (JWST) will allow observations of high-redshift galaxies at fainter detection levels than ever before, and JWST surveys targeting gravitationally lensed fields are expected to bring z ≳ 6 objects with very low star formation rate (SFR) within reach of spectroscopic studies. As galaxies at lower and lower star formation activity are brought into view, many of the standard methods used in the analysis of integrated galaxy spectra are at some point bound to break down, due to violation of the assumptions of a well-sampled stellar initial mass function (IMF) and a slowly varying SFR. We argue that galaxies with SFR ∼ 0.1 M⊙ yr−1 are likely to turn up at the spectroscopic detection limit of JWST in lensed fields, and investigate to what extent star formation sampling may affect the spectral analysis of such objects. We use the slug spectral synthesis code to demonstrate that such effects are likely to have significant impacts on spectral diagnostics of, for example, the Balmer emission lines. These effects are found to stem primarily from SFRs varying rapidly on short (∼Myr) time-scales due to star formation in finite units (star clusters), whereas the effects of an undersampled IMF is deemed insignificant in comparison. In contrast, the ratio between the He ii- and H i-ionizing flux is found to be sensitive to IMF-sampling as well as ICMF-sampling (sampling of the initial cluster mass function), which may affect interpretations of galaxies containing Population III stars or other sources of hard ionizing radiation.

scholarly journals Serendipitous discovery of an “ALMA-only” galaxy at 5 < z < 6 in an ALMA 3-mm survey

2019 ◽  
Vol 15 (S352) ◽  
pp. 194-198
Author(s):  
Christina C. Williams
Keyword(s):  
Star Formation ◽  
Energy Distribution ◽  
Star Formation Rate ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Spectral Energy ◽  
Large Contribution ◽  
Massive Galaxies ◽  
Multi Wavelength

AbstractWe discuss the serendipitous discovery of a dusty high-redshift galaxy in a small (8 arcmin2) ALMA 3-mm survey Williams et al. (2019). The galaxy was previously unknown and is absent from existing multi-wavelength catalogs (“ALMA-only”). Using the ALMA position as prior, we perform forced deblended photometry to constrain its spectral energy distribution. The spectral energy distribution is well described by a massive (M* = 1010.8 M⊙) and highly obscured (AV ∼ 4) galaxy at redshift z = 5.5 ± 1.1 with star formation rate ∼ 300 M⊙yr−1. Our small survey area implies an uncertain but large contribution to the cosmic star formation rate density, similar to the contribution from all ultraviolet-selected galaxies combined at this redshift. This galaxy likely traces an abundant population of massive galaxies absent from current samples of infrared-selected or sub-millimeter galaxies, but with larger space densities, higher duty cycles, and significant contribution to the cosmic star-formation rate and stellar mass densities.

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).

scholarly journals Recent star formation in the Hi dominated outer regions of early-type galaxies

2016 ◽  
Vol 11 (S321) ◽  
pp. 279-279
Author(s):  
Mustafa K. Yıldız ◽  
Paolo Serra ◽  
Reynier F. Peletier ◽  
Tom A. Oosterloo ◽  
Pierre-Alain Duc
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Radial Profile ◽  
Control Sample ◽  
Neutral Hydrogen ◽  
Stellar Mass ◽  
Early Type ◽  
Stellar Kinematics ◽  
The Impact

AbstractContextAccording to the ATLAS3D project, about 20 percent of all nearby early-type galaxies (D < 42 Mpc; MK < -21.5 mag; stellar mass Mstars ≳ 6 × 109 M⊙) outside clusters are surrounded by a disc or ring of low-column-density neutral hydrogen (Hi) gas with typical radii of tens of kpc, much larger than the stellar body.AimsOur aim is to understand the impact of these gas systems on the host galaxies, in particular, whether there is any recent star formation related to the Hi and effect of recent star formation on the host early-type galaxies.Methods and sampleWe analyse the distribution of star formation out to large radii by using resolved Hi images together with UV and optical images. We calculate the UV-UV and UV-optical colours in two apertures, 1-3 and 3-10 Reff. Using FUV emission as a proxy for star formation, we also estimate the integrated star formation rate in the outer regions. Our sample consists of 18 Hi-rich galaxies as well as 55 control galaxies where no Hi has been detected. We select the control sample galaxies to match the Hi-rich galaxies in stellar mass, environment, distance and stellar kinematics.ResultsIn half of the Hi-rich galaxies the radial UV profile changes slope at the position of the Hi radial profile peak. We find that the FUV-NUV and UV-optical colours in the first and second apertures of the Hi-rich galaxies are on average 0.5 and 0.8 mag bluer than the Hi-poor ones, respectively. We also find that the Hi-rich early-type galaxies have colour gradients that are almost 2 times stronger than the Hi-poor ones. we estimate the integrated star formation rate in the outer regions (R > 1 Reff) to be on average ~ 6.1×10−3 M⊙ yr−1 for the Hi-rich galaxies. We find that the gas depletion time in the outermost region (3-10 Reff) is ~ 80 Gyrs, which is similar to that estimated for the outskirts of spirals.ConclusionsStudying the stellar populations in early type galaxies with and without Hi, we find that galaxies with Hi generally show UV and UV-Optical colours in the outer parts that are bluer than those of early-type galaxies without Hi. This shows that the Hi is actively involved in recent star formation. The star formation rate in the outer regions is too low to build a stellar disc, and therefore change the morphology of the host even when integrated over several Gyrs. Star formation in outermost regions does not depend on the type of the galaxies.

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.

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