An extension of the MILES library with derived Teff, log g, [Fe/H], and [α/Fe]

Abstract Extragalactic astronomy and stellar astrophysics are intrinsically related. In fact, the determination of important galaxy properties such as stellar masses, star formation histories or chemical abundances relies on the ability to model their stellar populations. One important ingredient of these models are stellar libraries. Empirical libraries must have a good coverage of Teff, [Z/H], and surface gravity, and have these parameters reliably determined. MILES is one of the most widely used empirical libraries. Here we present an extension of this library with 205 new stars especially selected to cover important regions of the parameter space, including metal poor stars down to [Fe/H] ∼ −1.0. We describe the observations and data reductions as well as a new determination of the stellar parameters, including [α/Fe] ratio. The new MILES library contains 1070 stars with homogeneous and reliable determination of [Fe/H], Teff, log g and [α/Fe] ratio.

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An older, more quiescent universe from panchromatic SED fitting of the 3D-HST survey

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009025 ◽

2019 ◽

Vol 15 (S352) ◽

pp. 99-102

Author(s):

Joel Leja ◽

Benjamin D. Johnson ◽

Charlie Conroy ◽

Pieter van Dokkum ◽

Joshua S. Speagle ◽

...

Keyword(s):

Star Formation ◽

Star Formation Rate ◽

Formation Rate ◽

Complex Scaling ◽

Physical Systems ◽

Scaling Relationships ◽

Highly Correlated ◽

Bayesian Inference Framework ◽

Stellar Masses ◽

Star Formation Histories

AbstractGalaxies are complicated physical systems which obey complex scaling relationships; as a result, properties measured from broadband photometry are often highly correlated, degenerate, or both. Therefore, the accuracy of basic properties like stellar masses and star formation rates (SFRs) depend on the accuracy of many second-order galaxy properties, including star formation histories (SFHs), stellar metallicities, dust properties, and many others. Here, we re-assess measurements of galaxy stellar masses and SFRs using a 14-parameter physical model built in the Prospector Bayesian inference framework. We find that galaxies are ∼0.2 dex more massive and have ∼0.2 dex lower star formation rates than classic measurements. These measurements lower the observed cosmic star formation rate density and increase the observed buildup of stellar mass, finally bringing these two metrics into agreement at the factor-of-two level at 0.5 < z < 2.5.

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A redshift-dependent IRX–β dust attenuation relation for TNG50 galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1900 ◽

2020 ◽

Vol 497 (4) ◽

pp. 4773-4794 ◽

Cited By ~ 1

Author(s):

Sebastian Schulz ◽

Gergö Popping ◽

Annalisa Pillepich ◽

Dylan Nelson ◽

Mark Vogelsberger ◽

...

Keyword(s):

Star Formation ◽

Galaxy Formation ◽

Main Sequence ◽

Infrared Excess ◽

Star Forming ◽

Dust Composition ◽

Metal Ratio ◽

Stellar Masses ◽

Dust Attenuation ◽

Star Formation Histories

ABSTRACT We study the relation between the UV slope, β, and the ratio between the infrared- and UV luminosities (IRX) of galaxies from TNG50, the latest installment of the IllustrisTNG galaxy formation simulations. We select 7280 star-forming main-sequence (SFMS) galaxies with stellar mass ≥109 M⊙ at redshifts 0 ≤ z ≤ 4 and perform radiative transfer with skirt to model effects of interstellar medium dust on the emitted stellar light. Assuming a Milky Way dust type and a dust-to-metal ratio of 0.3, we find that TNG50 SFMS galaxies generally agree with observationally derived IRX–β relations at z ≲ 1. However, we find a redshift-dependent systematic offset with respect to empirically derived local relations, with the TNG50 IRX–β relation shifting towards lower β and steepening at higher redshifts. This is partially driven by variations in the dust-uncorrected UV slope of galaxies, due to different star formation histories of galaxies selected at different cosmic epochs; we suggest the remainder of the effect is caused by differences in the effective dust attenuation curves of galaxies as a function of redshift. We find a typical galaxy-to-galaxy variation of 0.3 dex in infrared excess (IRX) at fixed β, correlated with intrinsic galaxy properties: galaxies with higher star formation rates, star formation efficiencies, gas metallicities and stellar masses exhibit larger IRX values. We demonstrate a degeneracy between stellar age, dust geometry, and dust composition: z = 4 galaxies with a Small Magellanic Cloud dust type follow the same IRX–β relation as low-redshift galaxies with MW dust. We provide a redshift-dependent fitting function for the IRX–β relation for MW dust based on our models.

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Spectral synthesis of stellar populations in the 3D era: The CALIFA experience

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314009387 ◽

2014 ◽

Vol 10 (S309) ◽

pp. 93-98

Author(s):

R. Cid Fernandes ◽

E. A. D. Lacerda ◽

R. M. González Delgado ◽

N. Vale Asari ◽

R. García-Benito ◽

...

Keyword(s):

Star Formation ◽

Galaxy Evolution ◽

Spectral Synthesis ◽

Mass Density ◽

Formation Rate ◽

Stellar Populations ◽

Data Cubes ◽

The Mean ◽

Stellar Masses ◽

Star Formation Histories

AbstractMethods to recover the fossil record of galaxy evolution encoded in their optical spectra have been instrumental in processing the avalanche of data from mega-surveys along the last decade, effectively transforming observed spectra onto a long and rich list of physical properties: from stellar masses and mean ages to full star formation histories. This promoted progress in our understanding of galaxies as a whole. Yet, the lack of spatial resolution introduces undesirable aperture effects, and hampers advances on the internal physics of galaxies. This is now changing with 3D surveys. The mapping of stellar populations in data-cubes allows us to figure what comes from where, unscrambling information previously available only in integrated form. This contribution uses our starlight-based analysis of 300 CALIFA galaxies to illustrate the power of spectral synthesis applied to data-cubes. The selected results highlighted here include: (a) The evolution of the mass-metallicity and mass-density-metallicity relations, as traced by the mean stellar metallicity. (b) A comparison of star formation rates obtained from Hα to those derived from full spectral fits. (c) The relation between star formation rate and dust optical depth within galaxies, which turns out to mimic the Schmidt-Kennicutt law. (d) PCA tomography experiments.

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Outflows in low-mass galaxies at z >1

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316011686 ◽

2016 ◽

Vol 11 (S321) ◽

pp. 339-341

Author(s):

Michael V. Maseda ◽

Keyword(s):

Star Formation ◽

High Redshift ◽

Theoretical Models ◽

Potential Wells ◽

Low Mass ◽

Hydrodynamical Simulations ◽

Gas Accretion ◽

Stellar Masses ◽

Star Formation Histories ◽

Cold Gas

AbstractStar formation histories of local dwarf galaxies, derived through resolved stellar populations, appear complex and varied. The general picture derived from hydrodynamical simulations is one of cold gas accretion and bursty star formation, followed by feedback from supernovae and winds that heat and eject the central gas reservoirs. This ejection halts star formation until the material cools and re-accretes, resulting in an episodic SFH, particularly at stellar masses below ~ 109 M⊙. Such feedback has often been cited as the driving force behind the observed slowly-rising rotation curves in local dwarfs, due to an under-density of dark matter compared to theoretical models, which is one of the primary challenges to LCDM cosmology. However, these events have not yet been directly observed at high-redshift. Recently, using HST imaging and grism spectroscopy, we have uncovered an abundant population of low-mass galaxies (M* < 109 M⊙) at z = 1 - 2 that are undergoing strong bursts of star formation, in agreement with the theoretical predictions. These Extreme Emission Line Galaxies, with high specific SFRs and shallow gravitational potential wells, are ideal places to test the theoretical prediction of strong feedback-driven outflows. Here we use deep MUSE spectroscopy to search these galaxies for signatures of outflowing material, namely kinematic offsets between absorption lines (in the restframe optical and UV), which trace cool gas, and the nebular emission lines, which define the systemic redshift of the galaxy. Although the EELGs are intrinsically very faint, stacked spectra reveal blueshifted velocity centroids for Fe II absorption, which is indicative of outflowing cold gas. This represents the first constraint on outflows in M* < 109 M⊙ galaxies at z = 1 - 2. These outflows should regulate the star formation histories of low-mass galaxies at early cosmic times and thus play a crucial role in galaxy growth and evolution.

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Rejuvenated galaxies with very old bulges at the origin of the bending of the main sequence and of the ‘green valley’

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2130 ◽

2019 ◽

Vol 489 (1) ◽

pp. 1265-1290 ◽

Cited By ~ 8

Author(s):

Chiara Mancini ◽

Emanuele Daddi ◽

Stéphanie Juneau ◽

Alvio Renzini ◽

Giulia Rodighiero ◽

...

Keyword(s):

Star Formation ◽

Main Sequence ◽

Formation Rate ◽

Very Old ◽

Massive Galaxies ◽

Star Forming ◽

Late Event ◽

Age Of The Universe ◽

Stellar Masses ◽

Star Formation Histories

ABSTRACT We investigate the nature of star-forming galaxies with reduced specific star formation rate (sSFR) and high stellar masses, those ‘green valley’ objects that seemingly cause a reported bending, or flattening, of the star-forming main sequence. The fact that such objects host large bulges recently led some to suggest that the internal formation of bulges was a late event that induced the sSFRs of massive galaxies to drop in a slow downfall, and thus the main sequence to bend. We have studied in detail a sample of 10 galaxies at 0.45 < z < 1 with secure SFR from Herschel, deep Keck optical spectroscopy, and HST imaging from CANDELS allowing us to perform multiwavelength bulge to disc decomposition, and to derive star formation histories for the separated bulge and disc components. We find that the bulges hosted in these systems below main sequence are virtually all maximally old, with ages approaching the age of the Universe at the time of observation, while discs are young (〈 T50〉 ∼ 1.5 Gyr). We conclude that, at least based on our sample, the bending of the main sequence is, for a major part, due to rejuvenation, and we disfavour mechanisms that postulate the internal formation of bulges at late times. The very old stellar ages of our bulges suggest a number density of early-type galaxies at z = 1–3 higher than actually observed. If confirmed, this might represent one of the first direct validations of hierarchical assembly of bulges at high redshifts.

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The Stellar Masses and Star Formation Histories of Galaxies atz≈ 6: Constraints fromSpitzerObservations in the Great Observatories Origins Deep Survey

The Astrophysical Journal ◽

10.1086/505487 ◽

2006 ◽

Vol 651 (1) ◽

pp. 24-40 ◽

Cited By ~ 106

Author(s):

Haojing Yan ◽

Mark Dickinson ◽

Mauro Giavalisco ◽

Daniel Stern ◽

Peter R. M. Eisenhardt ◽

...

Keyword(s):

Star Formation ◽

Deep Survey ◽

Stellar Masses ◽

Star Formation Histories

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Lyα-EMITTING GALAXIES ATz= 2.1: STELLAR MASSES, DUST, AND STAR FORMATION HISTORIES FROM SPECTRAL ENERGY DISTRIBUTION FITTING

The Astrophysical Journal ◽

10.1088/0004-637x/733/2/114 ◽

2011 ◽

Vol 733 (2) ◽

pp. 114 ◽

Cited By ~ 64

Author(s):

Lucia Guaita ◽

Viviana Acquaviva ◽

Nelson Padilla ◽

Eric Gawiser ◽

Nicholas A. Bond ◽

...

Keyword(s):

Star Formation ◽

Energy Distribution ◽

Spectral Energy Distribution ◽

Spectral Energy ◽

Distribution Fitting ◽

Stellar Masses ◽

Star Formation Histories

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Evolution histories of massive galaxies at z∼2 over the past 3 Gyr

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319002734 ◽

2019 ◽

Vol 15 (S341) ◽

pp. 50-54

Author(s):

T. Morishita ◽

L. E. Abramson ◽

T. Treu ◽

G. B. Brammer ◽

T. Jones ◽

...

Keyword(s):

Star Formation ◽

Gas Phase ◽

Early Type ◽

Imaging Data ◽

Data Set ◽

Massive Galaxies ◽

Star Forming ◽

The Past ◽

Star Formation Histories

AbstractWe study star formation and metallicity enrichment histories of 24 massive galaxies at 1.6 < z < 2.5. Deep slitless spectroscopy + imaging data set collected from multiple HST surveys allows robust determination of their SEDs. Our new SED modeling with no functional assumptions on star formation histories revels that 1. most of the sample galaxies have already formed >50% of their extant masses ∼1.5 Gyr before the time of observed redshifts, with a trend where more massive galaxies form earlier, 2. most of our galaxies already have stellar metallicities compatible with those of local early-type galaxies, and 3. inferred metallicities are on average ∼ 0.25 dex higher than observed gas-phase metallicities of star forming galaxies at the time of their formation. Continuation of low-level star formation, rather than abrupt termination of star forming activity, may explain the observed gap of metallicities.

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Damped Lyα systems as probes of chemical evolution over cosmological timescales

Proceedings of the International Astronomical Union ◽

10.1017/s174392130802468x ◽

2008 ◽

Vol 4 (S255) ◽

pp. 121-128

Author(s):

Miroslava Dessauges-Zavadsky

Keyword(s):

Star Formation ◽

High Redshift ◽

Large Contribution ◽

High Redshift Galaxies ◽

Star Forming ◽

Current State ◽

Galaxy Population ◽

Stellar Masses ◽

Star Formation Histories ◽

Redshift Galaxies

AbstractWe review the current state of knowledge of damped Lyα systems (DLAs) selected in absorption on quasar sightlines. These objects are extremely useful to study the interstellar medium of high-redshift galaxies and the nucleosynthesis in the early Universe. The characteristics of this galaxy population has been investigated for years and slowly we are getting information on their puzzling nature. Imaging atz<1 shows that DLAs are associated with a mixing bag of galaxies with no especially large contribution from dwarf galaxies. Evidence for a mild evolution of the cosmic mean metallicity with time is observed. The star formation histories of these high-redshift galaxies begin to be accessible and indicate that DLAs tend to be young, gas-dominated galaxies with low star formation rates per unit area. Finally, indirect estimation of the DLA stellar masses from the mass-metallicity relations observed for emission-selected star-forming galaxies atz= 2−3 points to intermediate-mass galaxies withM*< 109M⊙.

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