scholarly journals Insights into star cluster formation from λ ≳ 1μm

2009 ◽  
Vol 5 (S266) ◽  
pp. 177-183
Author(s):  
Rémy Indebetouw ◽  
Rosie Chen ◽  
Crystal Brogan ◽  
Barbara Whitney ◽  
Thomas Robitaille ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Stars ◽  
Cluster Formation ◽  
Spectral Energy Distribution ◽  
Infrared Emission ◽  
Star Formation History ◽  
Young Stellar Objects ◽  
Circumstellar Dust ◽  
Spectral Energy ◽  
Evolutionary State

AbstractWe would like to know how molecular clouds turn into stellar clusters, and with what efficiency massive stars form in those clusters, since massive stars are the main agents responsible for evolution of the interstellar medium of galaxies, and their subsequent star-formation history. The imprint of ‘precluster’ molecular cloud conditions can be observed, but only in the least evolved, most embedded clusters, necessarily at wavelengths that can penetrate more than 10 visual magnitudes of extinction. Mid-infrared photometric imaging, most recently and extensively from Spitzer, can be used to select young stellar objects in clustered star-formation environments in our Galaxy and nearby galaxies. Relatively sophisticated methods have been developed, but the fundamental principle remains the selection of sources that have excess infrared emission from circumstellar dust. By fitting radiative-transfer models to a source's spectral-energy distribution between ~1 and ~100μm, we constrain the circumstellar dust distribution and evolutionary state. We can explore many things with this protostellar distribution in mass/luminosity and time/evolutionary state. For example we do not see strong evidence for primordial mass segregation in initial studies. We find evidence of primordial hierarchical substructure, greater clustering at the youngest stages, and even imprints of the pre-stellar Jeans scale. We see correlation of the youngest sources with dense molecular clumps and constrain the timescales for chemical processing and dispersal of those clumps. We have only begun to mine the wealth of existing Spitzer, emerging Herschel and soon ALMA data.

scholarly journals The effects of star formation history in the SFR–M* relation of H ii galaxies

2020 ◽  
Vol 500 (3) ◽  
pp. 3240-3253
Author(s):  
Amanda R Lopes ◽  
Eduardo Telles ◽  
Jorge Melnick
Keyword(s):  
Star Formation ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Star Formation History ◽  
Spectral Energy ◽  
Distribution Fitting ◽  
Good Tool ◽  
Star Forming ◽  
Additional Information ◽  
Star Formation Histories

ABSTRACT We discuss the implications of assuming different star formation histories (SFH) in the relation between star formation rate (SFR) and mass derived by the spectral energy distribution fitting (SED). Our analysis focuses on a sample of H ii galaxies, dwarf starburst galaxies spectroscopically selected through their strong narrow emission lines in SDSS DR13 at z < 0.4, cross-matched with photometric catalogues from GALEX, SDSS, UKIDSS, and WISE. We modelled and fitted the SEDs with the code CIGALE adopting different descriptions of SFH. By adding information from different independent studies, we find that H ii galaxies are best described by episodic SFHs including an old (10 Gyr), an intermediate age (100−1000 Myr) and a recent population with ages < 10 Myr. H ii galaxies agree with the SFR−M* relation from local star-forming galaxies, and only lie above such relation when the current SFR is adopted as opposed to the average over the entire SFH. The SFR−M* demonstrated not to be a good tool to provide additional information about the SFH of H ii galaxies, as different SFH present a similar behaviour with a spread of <0.1 dex.

scholarly journals Surrogate modelling the Baryonic Universe – I. The colour of star formation

2020 ◽  
Vol 495 (2) ◽  
pp. 2088-2104
Author(s):  
Jonás Chaves-Montero ◽  
Andrew Hearin
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Principal Component ◽  
Major Axis ◽  
Sloan Digital Sky Survey ◽  
Star Formation History ◽  
Spectral Energy ◽  
Colour Space

ABSTRACT The spectral energy distribution of a galaxy emerges from the complex interplay of many physical ingredients, including its star formation history (SFH), metallicity evolution, and dust properties. Using galaxpy, a new galaxy spectral prediction tool, and SFHs predicted by the empirical model universemachine and the cosmological hydrodynamical simulation IllustrisTNG, we isolate the influence of SFH on optical and near-infrared colours from 320 to 1080 Å at z = 0. By carrying out a principal component analysis, we show that physically motivated SFH variations modify galaxy colours along a single direction in colour space: the SFH-direction. We find that the projection of a galaxy’s present-day colours on to the SFH-direction is almost completely regulated by the fraction of stellar mass that the galaxy formed over the last billion years. Together with cosmic downsizing, this results in galaxies becoming redder as their host halo mass increases. We additionally study the change in galaxy colours due to variations in metallicity, dust attenuation, and nebular emission lines, finding that these properties vary broad-band colours along distinct directions in colour space relative to the SFH-direction. Finally, we show that the colours of low-redshift Sloan Digital Sky Survey galaxies span an ellipsoid with significant extent along two independent dimensions, and that the SFH-direction is well-aligned with the major axis of this ellipsoid. Our analysis supports the conclusion that variations in SFH are the dominant influence on present-day galaxy colours, and that the nature of this influence is strikingly simple.

scholarly journals Multiwavelength radio observations of a brightest cluster galaxy at z = 1.71: detection of a modest active galactic nucleus and evidence for extended star formation

2019 ◽  
Vol 487 (1) ◽  
pp. 1210-1217 ◽  
Author(s):  
Ariane Trudeau ◽  
Tracy Webb ◽  
Julie Hlavacek-Larrondo ◽  
Allison Noble ◽  
Marie-Lou Gendron-Marsolais ◽  
...  
Keyword(s):  
Star Formation ◽  
Active Galactic Nucleus ◽  
Spectral Energy Distribution ◽  
Galaxy Cluster ◽  
Far Infrared ◽  
Infrared Emission ◽  
Spectral Energy ◽  
Radio Observations ◽  
Cluster Galaxy ◽  
Star Forming

ABSTRACT We present deep, multiwavelength radio observations of SpARCS104922.6 + 564032.5, a z = 1.71 galaxy cluster with a starbursting core. Observations were made with the Karl G. Jansky Very Large Array (JVLA) in three bands: 1–2 GHz, 4–8 GHz, and 8–12 GHz. We detect a radio source coincident with the brightest cluster galaxy (BCG) that has a spectral index of α = 0.44 ± 0.29 and is indicative of emission from an active galactic nucleus. The radio luminosity is consistent with the average luminosity of the lower redshift BCG sample, but the flux densities are 6σ below the predicted values of the star-forming spectral energy distribution based on far infrared data. Our new fit fails to simultaneously describe the far infrared and radio fluxes. This, coupled with the fact that no other bright source is detected in the vicinity of the BCG implies that the star formation region, traced by the infrared emission, is extended or clumpy and not located directly within the BCG. Thus, we suggest that the star-forming core might not be driven by a single major wet merger, but rather by several smaller galaxies stripped of their gas or by a displaced cooling flow, although more data are needed to confirm any of those scenarios.

scholarly journals Galaxy And Mass Assembly (GAMA): a forensic SED reconstruction of the cosmic star formation history and metallicity evolution by galaxy type

2020 ◽  
Vol 498 (4) ◽  
pp. 5581-5603
Author(s):  
Sabine Bellstedt ◽  
Aaron S G Robotham ◽  
Simon P Driver ◽  
Jessica E Thorne ◽  
Luke J M Davies ◽  
...  
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Mass Density ◽  
Spectral Energy Distribution ◽  
Stellar Mass ◽  
Star Formation History ◽  
Spectral Energy ◽  
Massive Galaxies ◽  
Formation History ◽  
The Universe

ABSTRACT We apply the spectral energy distribution (SED) fitting code ProSpect to multiwavelength imaging for ∼7000 galaxies from the GAMA survey at z < 0.06, in order to extract their star formation histories. We combine a parametric description of the star formation history with a closed-box evolution of metallicity where the present-day gas-phase metallicity of the galaxy is a free parameter. We show with this approach that we are able to recover the observationally determined cosmic star formation history (CSFH), an indication that stars are being formed in the correct epoch of the Universe, on average, for the manner in which we are conducting SED fitting. We also show the contribution to the CSFH of galaxies of different present-day visual morphologies and stellar masses. Our analysis suggests that half of the mass in present-day elliptical galaxies was in place 11 Gyr ago. In other morphological types, the stellar mass formed later, up to 6 Gyr ago for present-day irregular galaxies. Similarly, the most massive galaxies in our sample were shown to have formed half their stellar mass by 11 Gyr ago, whereas the least massive galaxies reached this stage as late as 4 Gyr ago (the well-known effect of ‘galaxy downsizing’). Finally, our metallicity approach allows us to follow the average evolution in gas-phase metallicity for populations of galaxies and extract the evolution of the cosmic metal mass density in stars and in gas, producing results in broad agreement with independent, higher redshift observations of metal densities in the Universe.

scholarly journals Local Analogs to High-redshift Galaxies. I. Characterization of Dust Emission and Star Formation History

2021 ◽  
Vol 921 (2) ◽  
pp. 130
Author(s):  
Skarleth M. Motiño Flores ◽  
Tommy Wiklind ◽  
Rafael T. Eufrasio
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Star Formation History ◽  
Spectral Energy ◽  
High Redshift Galaxies ◽  
Star Formation Activity ◽  
Look Back ◽  
Redshift Galaxies

Abstract Star-forming dwarf galaxies have properties similar to those expected in high-redshift galaxies. Hence, these local galaxies may provide insights into the evolution of the first galaxies and the physical processes at work. We present a sample of 11 potential local analogs to high-z (LAHz) galaxies. The sample consists of blue compact dwarf galaxies, selected to have spectral energy distributions that fit galaxies at 1.5 < z < 4. We use SOFIA-HAWC+ observations combined with optical and near-infrared data to characterize the dust properties, star formation rate (SFR), and star formation histories (SFHs) of the sample of LAHz galaxies. We employ Bayesian analysis to characterize the dust using two-component blackbody models. Using the Lightning package, we fit the spectral energy distribution of the LAHz galaxies over the far-UV−far-infrared wavelength range and derive the SFH in five time steps up to a look-back time of 13.3 Gyr. Of the 11 LAHz candidates, six galaxies have SFH consistent with no star formation activity at look-back times beyond 1 Gyr. The remaining galaxies show residual levels of star formation at ages ≳1 Gyr, making them less suitable as local analogs. The six young galaxies stand out in our sample by having the lowest gas-phase metallicities. They are characterized by warmer dust, having the highest specific SFR and the highest gas mass fractions. The young age of these six galaxies suggests that merging is less important as a driver of the star formation activity. The six LAHz candidates are promising candidates for studies of the gasdynamics role in driving star formation.

scholarly journals Exploring the star formation histories of galaxies in different environments from MaNGA spectra

2019 ◽  
Vol 15 (S341) ◽  
pp. 60-64
Author(s):  
Maria Argudo-Fernández ◽  
Médéric Boquien ◽  
Shiyin Shen ◽  
Fangting Yuan ◽  
Jun Yin ◽  
...  
Keyword(s):  
Star Formation ◽  
Spectral Energy Distribution ◽  
Star Formation History ◽  
Spectral Energy ◽  
New Techniques ◽  
Secular Evolution ◽  
Isolated Galaxies ◽  
Multi Wavelength ◽  
Field Unit ◽  
High Level

AbstractThe star formation history (SFH) of galaxies allow us to investigate when galaxies formed their stars and assembled their mass. We can constrain the SFH with high level of precision from galaxies with resolved stellar populations, since we are able to discriminate between stars of different ages from the spectrum they emit. However, the relative importance of secular evolution (nature) over nurture is not yet clear, and separating the effects of interaction-driven evolution in the observed galaxy properties is not trivial. The aim of this study is to use MaNGA (Mapping Nearby Galaxies at APO) Integral Field Unit (IFU) data, in combination with multi-wavelength data, to constrain the SFH of nearby isolated galaxies. We present here the new techniques we are developing to constrain the SFH with high level of precision from Spectral Energy Distribution (SED) fitting. This study is part of a China-Chile collaboration program where we are applying these new techniques to investigate how galaxies formed and evolve in different environments.

scholarly journals Cosmic infrared background measurements and star formation history from Planck

2014 ◽  
Vol 10 (S306) ◽  
pp. 144-146
Author(s):  
Paolo Serra ◽  
Keyword(s):  
Star Formation ◽  
Power Spectrum ◽  
Signal To Noise Ratio ◽  
Spectral Energy Distribution ◽  
Power Spectra ◽  
Star Formation History ◽  
Spectral Energy ◽  
Formation History ◽  
Infrared Background ◽  
Cosmic Infrared Background

AbstractWe present new measurements of Cosmic Infrared Background (CIB) anisotropies using Planck. Combining HFI data with IRAS, the angular auto- and cross-frequency power spectrum is measured from 143 to 3000 GHz. After careful removal of the contaminants (cosmic microwave background anisotropies, Galactic dust and Sunyaev-Zeldovich emission), and a complete study of systematics, the CIB power spectrum is measured with unprecedented signal to noise ratio from angular multipoles ℓ ~ 150 to 2500. The interpretation based on the halo model is able to associate star-forming galaxies with dark matter halos and their subhalos, using a parametrized relation between the dust-processed infrared luminosity and (sub-)halo mass, and it allows to simultaneously fit all auto- and cross- power spectra very well. We find that the star formation history is well constrained up to redshifts around 2, and agrees with recent estimates of the obscured star-formation density using Spitzer and Herschel. However, at higher redshift, the accuracy of the star formation history measurement is strongly degraded by the uncertainty in the spectral energy distribution of CIB galaxies. We also find that the mean halo mass which is most efficient at hosting star formation is log(Meff/M⊙) = 12.6 and that CIB galaxies have warmer temperatures as redshift increases.

scholarly journals Kinematics and dynamics of the luminous infrared galaxy pair NGC 5257/58 (Arp 240)

2018 ◽  
Vol 621 ◽  
pp. A25 ◽  
Author(s):  
I. Fuentes-Carrera ◽  
M. Rosado ◽  
P. Amram ◽  
E. Laurikainen ◽  
H. Salo ◽  
...  
Keyword(s):  
Star Formation ◽  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Star Formation History ◽  
Spectral Energy ◽  
Kinematics And Dynamics ◽  
Ionized Gas ◽  
Star Forming ◽  
External Perturbations ◽  
Formation History

Context. Encounters between galaxies modify their morphology, kinematics, and star formation history. The relation between these changes and external perturbations is not straightforward. The great number of parameters involved requires both the study of large samples and individual encounters where particular features, motions, and perturbations can be traced and analysed in detail. Aims. We analysed the morphology, kinematics, and dynamics of two luminous infrared spiral galaxies of almost equal mass, NGC 5257 and NGC 5258, in which star formation is mostly confined to the spiral arms, in order to understand interactions between galaxies of equivalent masses and star-forming processes during the encounter. Methods. Using scanning Fabry–Perot interferometry, we studied the contribution of circular and non-circular motions and the response of the ionized gas to external perturbations. We compared the kinematics with direct images and traced the star-forming processes and gravitational effects due to the presence of the other galaxy. The spectral energy distribution of each member of the pair was fitted. A mass model was fitted to the rotation curve of each galaxy. Results. Large, non-circular motions detected in both galaxies are associated with a bar, spiral arms, and HII regions for the inner parts of the galaxies, and with the tidal interaction for the outer parts of the discs. Bifurcations in the rotation curves indicate that the galaxies have recently undergone pericentric passage. The pattern speed of a perturbation of one of the galaxies is computed. Location of a possible corotation seems to indicate that the gravitational response of the ionized gas in the outer parts of the disc is related to the regions where ongoing star formation is confined. The spectral energy distribution fit indicates slightly different star formation history for each member of the pair. For both galaxies, a pseudo-isothermal halo better fits the global mass distribution.

scholarly journals The molecular cloud and embedded young stellar population associated with IRAS 18236–1205

2009 ◽  
Vol 5 (S266) ◽  
pp. 516-516
Author(s):  
Ricardo Retes ◽  
Abraham Luna ◽  
Divakara Mayya ◽  
Luis Carrasco
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Massive Star ◽  
Stellar Population ◽  
Spectral Energy Distribution ◽  
Point Sources ◽  
Young Stellar Objects ◽  
Spectral Energy ◽  
Massive Star Formation ◽  
Iras Source

AbstractWe test a membership method to select embedded young stellar objects (YSOs) from a Galactic molecular cloud with ongoing massive star formation using multiband analysis. We select and discuss the embedded stellar population in the molecular cloud associated with IRAS 18235−1205, a small, geometrically well-defined Galactic molecular cloud. The IRAS source has infrared fluxes characteristic of an UCHii region, CS(J = 2 − 1) emission, and methanol and water maser emission, suggesting that this region is a good candidate for studies of young, massive star formation. The selection method of embedded stellar populations is based on the spatial distribution of 13CO(J = 1 − 0) and Spitzer/MIPS 24 μm point sources. Photometric analysis using near/mid-infrared images are used to test our selection criteria. Three objects are associated with the IRAS source; two have a characteristic spectral-energy distribution (SED) of a Class I/0 object (protostar) and the third has an SED of Class II.

scholarly journals Stellar populations of HII galaxies

2018 ◽  
Vol 615 ◽  
pp. A55 ◽  
Author(s):  
Eduardo Telles ◽  
Jorge Melnick
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Spectral Energy Distribution ◽  
Age Determination ◽  
Stellar Mass ◽  
Star Formation History ◽  
Spectral Energy ◽  
Model Parameters ◽  
Formation History ◽  
Star Formation Histories

Aims. We present a UV to mid-IR spectral energy distribution (SED) study of a large sample of SDSS DR13 HII galaxies. These galaxies are selected as starbursts (EW(Hα) > 50Å) and for their high-excitation locus in the upper left region of the BPT diagram. Their photometry was derived from the cross-matched GALEX, SDSS, UKDISS, and WISE catalogs. Methods. We used CIGALE modeling and a SED fitting routine with the parametrization of a three-burst star formation history, and a comprehensive analysis of all other model parameters. We were able to estimate the contribution of the underlying old stellar population to the observed equivalent width of Hβ, and allow for more accurate burst age determination. Results. We found that the star formation histories of HII Galaxies can be reproduced remarkably well by three major eras of star formation. In addition, the SED fitting results indicate that in all cases the current burst produces a small percent of the total stellar mass, i.e., the bulk of stellar mass in HII galaxies has been produced by the past episodes of star formation, and also indicate that at a given age the Hβ luminosity depends only on the mass of young stars favoring a universal IMF for massive stars. Most importantly, the current star formation episodes are maximum starbursts that produce stars at the highest possible rate.

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