Ecology of galaxy stellar populations from optical spectroscopic surveys

AbstractThe age and chemical composition of the stars in present-day galaxies carry important clues about their star formation processes. The latest generation of population synthesis models have allowed to derive age and stellar metallicity estimates for large samples of low-redshift galaxies. After reviewing the main results about the distribution in ages and metallicities as a function of galaxy mass, I will concentrate on recent analysis that aims at disentangling the dependences of stellar populations properties on environment and on galaxy stellar mass. Finally, new models that predict the response of the full spectrum to variations in [α/Fe] will allow us to derive accurate estimates of elements abundance ratios and gain deeper insight into the timescales of star formation cessation.

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Michigan 160: a precursor to the LMC?

Symposium - International Astronomical Union ◽

10.1017/s0074180900200910 ◽

1991 ◽

Vol 148 ◽

pp. 376-377

Author(s):

L. Staveley-Smith

Keyword(s):

Star Formation ◽

Dynamical Evolution ◽

Stellar Populations ◽

Detailed Comparison ◽

Elliptical Galaxies ◽

Magellanic Clouds ◽

Formation Processes ◽

Stellar Formation ◽

The Galaxy ◽

Magellanic Stream

The tidal interaction between the Magellanic Clouds and the Galaxy is an important factor in influencing the physical and dynamical evolution of the Clouds (e.g. the Magellanic Stream) as well as the genesis and evolution of their respective stellar populations. However, how important is the influence of the Galaxy? This is a key question since we know that relatively isolated, magellanic-type galaxies do exist (e.g. NGC 3109 and NGC 4449) and have been just as efficient at star-formation as the LMC. It is possible in fact that the star formation in the clouds is primarily stochastic in nature and is relatively insensitive to the global forces which seem to have shaped stellar formation processes in massive spiral and elliptical galaxies. Unsupported by a massive bulge or halo component, cold gas disks are inherently susceptible to radial and bar-like instabilities (Efstathiou et al. 1982) which are very efficient at creating the dynamical pressures required for rapid star-formation. With this in mind, a detailed comparison of 'field' magellanic-type galaxies with the LMC and SMC is of some importance.

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Binary fraction indicators in resolved stellar populations and supernova-type ratios

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2089 ◽

2020 ◽

Vol 497 (2) ◽

pp. 2201-2212 ◽

Cited By ~ 1

Author(s):

E R Stanway ◽

J J Eldridge ◽

A A Chrimes

Keyword(s):

Massive Star ◽

Stellar Population ◽

Stellar Populations ◽

Initial Mass ◽

Core Collapse ◽

Population Synthesis ◽

Large Samples ◽

Low Mass ◽

Galaxy Population ◽

Number Counts

ABSTRACT The binary fraction of a stellar population can have pronounced effects on its properties, and, in particular, the number counts of different massive star types, and the relative subtype rates of the supernovae (SNe) that end their lives. Here we use binary population synthesis models with a binary fraction that varies with initial mass to test the effects on resolved stellar pops and SNe, and ask whether these can constrain the poorly-known binary fraction in different mass and metallicity regimes. We show that Wolf–Rayet (WR) star subtype ratios are valuable binary diagnostics, but require large samples to distinguish by models. Uncertainties in which stellar models would be spectroscopically classified as WR stars are explored. The ratio of thermonuclear, stripped-envelope, and other core-collapse SNe may prove a more accessible test and upcoming surveys will be sufficient to constrain both the high- and low-mass binary fraction in the z < 1 galaxy population.

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The history of the Galactic bulge

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317000989 ◽

2016 ◽

Vol 12 (S323) ◽

pp. 184-187 ◽

Cited By ~ 1

Author(s):

A. A. Zijlstra ◽

K. Gesicki ◽

M. M. Miller Bertolami

Keyword(s):

Star Formation ◽

Planetary Nebulae ◽

Elliptical Galaxies ◽

Recent Analysis ◽

Galactic Bulge ◽

Luminosity Functions ◽

New Models ◽

Show Evidence ◽

History Of ◽

Star Formation Histories

AbstractPlanetary nebulae form in stellar populations with ages from 1 to 10 Gyr, and can be used to trace their star formation histories. Here we apply this to the Galactic bulge, where there are indications both for an old origin and for younger stars. We use new stellar models, which have significant different evolutionary speeds during the post-AGB phase. We apply these new models to a sample of 32 planetary nebulae with HST imaging and VLT spectroscopy. The results show evidence for an old starburst, followed by continuous star formation until at least 2Gyr ago. This agrees very well with recent analysis of colour-magnitude diagrams of the bulge. We show that the new models can also explain the [OIII] luminosity functions, and predict the uniform luminosity cut-off both in spiral galaxies and old elliptical galaxies.

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SDSS-IV MaNGA: spatially resolved dust attenuation in spiral galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1300 ◽

2020 ◽

Vol 495 (2) ◽

pp. 2305-2320

Author(s):

Michael J Greener ◽

Alfonso Aragón-Salamanca ◽

Michael R Merrifield ◽

Thomas G Peterken ◽

Amelia Fraser-McKelvie ◽

...

Keyword(s):

Star Formation ◽

Spiral Galaxies ◽

Formation Rate ◽

Stellar Populations ◽

High Concentration ◽

Full Spectrum ◽

Star Forming ◽

Spatially Resolved ◽

Radial Profiles ◽

Dust Attenuation

ABSTRACT Dust attenuation in star-forming spiral galaxies affects stars and gas in different ways due to local variations in dust geometry. We present spatially resolved measurements of dust attenuation for a sample of 232 such star-forming spiral galaxies, derived from spectra acquired by the SDSS-IV MaNGA survey. The dust attenuation affecting the stellar populations of these galaxies (obtained using full spectrum stellar population fitting methods) is compared with the dust attenuation in the gas (derived from the Balmer decrement). Both of these attenuation measures increase for local regions of galaxies with higher star formation rates; the dust attenuation affecting the stellar populations increases more so than the dust attenuation in the gas, causing the ratio of the dust attenuation affecting the stellar populations to the dust attenuation in the gas to decrease for local regions of galaxies with higher star formation rate densities. No systematic difference is discernible in any of these dust attenuation quantities between the spiral arm and interarm regions of the galaxies. While both the dust attenuation in the gas and the dust attenuation affecting the stellar populations decrease with galactocentric radius, the ratio of the two quantities does not vary with radius. This ratio does, however, decrease systematically as the stellar mass of the galaxy increases. Analysis of the radial profiles of the two dust attenuation measures suggests that there is a disproportionately high concentration of birth clouds (incorporating gas, young stars, and clumpy dust) nearer to the centres of star-forming spiral galaxies.

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Fundamental differences in the radio properties of red and blue quasars: enhanced compact AGN emission in red quasars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa954 ◽

2020 ◽

Vol 494 (4) ◽

pp. 4802-4818 ◽

Cited By ~ 2

Author(s):

V A Fawcett ◽

D M Alexander ◽

D J Rosario ◽

L Klindt ◽

S Fotopoulou ◽

...

Keyword(s):

Star Formation ◽

Radio Emission ◽

Sloan Digital Sky Survey ◽

Formation Processes ◽

Very Large Array ◽

Radio Detection ◽

Extended Radio ◽

Sky Survey ◽

Tentative Evidence ◽

Insight Into

ABSTRACT We have recently used the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey to show that red quasars have fundamentally different radio properties to typical blue quasars: a significant (factor ≈3) enhancement in the radio-detection fraction, which arises from systems around the radio-quiet threshold with compact (<5 arcsec) radio morphologies. To gain greater insight into these physical differences, here we use the DR14 Sloan Digital Sky Survey (SDSS) and more sensitive, higher resolution radio data from the Very Large Array (VLA) Stripe 82 (S82) and VLA-COSMOS 3 GHz (C3GHz) surveys. With the S82 data, we perform morphological analyses at a resolution and depth three times that of the FIRST radio survey, and confirm an enhancement in radio-faint and compact red quasars over typical quasars; we now also find tentative evidence for an enhancement in red quasars with slightly extended radio structures (16–43 kpc at z = 1.5). These analyses are complemented by C3GHz, which is deep enough to detect radio emission from star-formation processes. From our data we find that the radio enhancement from red quasars is due to AGN activity on compact scales (≲43 kpc) for radio-intermediate–radio-quiet sources (−5 < $\mathcal {R}$ < −3.4, where $\mathcal {R}$ = $L_{\rm{1.4\,GHz}}/L_{6\mu\text{m}}$), which decreases at $\mathcal {R}$ < −5 as the radio emission from star-formation starts to dilute the AGN component. Overall our results argue against a simple orientation scenario and are consistent with red quasars representing a younger, earlier phase in the overall evolution of quasars.

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Stellar Populations and Kinematics in Spiral Galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310002735 ◽

2009 ◽

Vol 5 (S262) ◽

pp. 172-175

Author(s):

Lauren A. MacArthur ◽

J. Jesús González ◽

Stéphane Courteau ◽

Michael McDonald

Keyword(s):

Star Formation ◽

Spiral Galaxies ◽

Broad Band ◽

Synthesis Method ◽

Stellar Populations ◽

Star Formation History ◽

Population Synthesis ◽

The Galaxy ◽

Single Burst ◽

Full Population

AbstractWe present a detailed study of the stellar populations (SPs) and kinematics of the bulge and inner disk regions of nearby spiral galaxies (Sa-Sd) based on deep long-slit Gemini/GMOS data. We find that the SPs of spiral galaxies are not well matched by single episodes of star formation; representative SPs must involve average SP values integrated over the star formation history (SFH) of the galaxy, such as those derived from the “full population synthesis” method used here. Our spiral bulges follow the same correlations of increasing light-weighted age and metallicity with central velocity dispersion as those of elliptical galaxies and early-type bulges found in other studies, but when SFHs more complex and realistic than a single burst are invoked, the trend with age is shallower and its scatter much reduced. In a mass-weighted context, all bulges are predominantly composed of old and metal-rich SPs. Bulge formation appears to be dominated by early processes that are common to all spheroids, whether they currently reside in disks or not. While monolithic collapse cannot be ruled out in some cases, merging must be invoked to explain the SP gradients in most bulges. Further bulge growth via secular processes, or “rejuvenated” star formation, generally contributes minimally to the stellar mass budget. We also demonstrate how the combination of our full population synthesis modeling of high-quality optical spectra of integrated SPs along with optical-NIR broad-band imaging can single out potential model weaknesses and help determine the reliability of the inferred SFHs.

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