Early Type Galaxies in the Mid Infrared: a new flavor to their stellar populations

The stellar initial mass function (IMF) is one of the fundamental pillars in studies of stellar populations. It is the mass distribution of stars at birth, and it is traditionally assumed to be universal, adopting generic functions constrained by resolved (i.e. nearby) stellar populations (e.g., Salpeter 1955; Kroupa 2001; Chabrier 2003). However, for the vast majority of cases, stars are not resolved in galaxies. Therefore, the interpretation of the photo-spectroscopic observables is complicated by the many degeneracies present between the properties of the unresolved stellar populations, including IMF, age distribution, and chemical composition. The overall good match of the photometric and spectroscopic observations of galaxies with population synthesis models, adopting standard IMF choices, made this issue a relatively unimportant one for a number of years. However, improved models and observations have opened the door to constraints on the IMF in unresolved stellar populations via gravity-sensitive spectral features. At present, there is significant evidence of a non-universal IMF in early-type galaxies (ETGs), with a trend towards a dwarf-enriched distribution in the most massive systems (see, e.g., van Dokkum & Conroy 2010; Ferreras et al. 2013; La Barbera et al. 2013). Dynamical and strong-lensing constraints of the stellar M/L in similar systems give similar results, with heavier M/L in the most massive ETGs (see, e.g., Cappellari et al. 2012; Posacki et al. 2015). Although the interpretation of the results is still open to discussion (e.g., Smith 2014; La Barbera 2015), one should consider the consequences of such a bottom-heavy IMF in massive galaxies.

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Star formation histories of resolved galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309031718 ◽

2008 ◽

Vol 4 (S258) ◽

pp. 61-72

Author(s):

Monica Tosi

Keyword(s):

Star Formation ◽

Observational Data ◽

Stellar Populations ◽

Morphological Type ◽

The Other ◽

Early Type ◽

Significant Rate ◽

Star Formation Histories

AbstractThe colour-magnitude diagrams of resolved stellar populations are the best tool to study the star formation histories of the host galactic regions. In this review the method to derive star formation histories by means of synthetic colour-magnitude diagrams is briefly outlined, and the results of its application to resolved galaxies of various morphological types are summarized. It is shown that all the galaxies studied so far were already forming stars at the lookback time reached by the observational data, independently of morphological type and metallicity. Early-type galaxies have formed stars predominantly, but in several cases not exclusively, at the earliest epochs. All the other galaxies appear to have experienced rather continuous star formation activities throughout their lifetimes, although with significant rate variations and, sometimes, short quiescent phases.

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Stellar Populations of the Most Massive Galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310007015 ◽

2009 ◽

Vol 5 (S267) ◽

pp. 459-459

Author(s):

Alexander Fritz ◽

Michael D. Hoenig ◽

Ricardo P. Schiavon

Keyword(s):

High Velocity ◽

Surface Brightness ◽

Stellar Populations ◽

Spectroscopic Properties ◽

Low Density ◽

Early Type ◽

Small Surface ◽

Fundamental Plane ◽

Massive Galaxies ◽

Bona Fide

Within the hierarchical CDM framework, gas-poor mergers contribute substantially to the building of the most massive galaxies (Faber et al. 2007). We want to test this scenario by studying the fundamental plane (FP) and the stellar populations of the most massive galaxies. We investigate a well-defined sample of massive early-type galaxies at 0.1<z<0.4, identified from the SDSS database. Out of 42,000 possible targets in the SDSS database, we extracted 23 luminous early-type galaxies with bona fide high velocity dispersions of σ>350 km s−1. These systems are located either in high or low-density environments and show a variety of small surface-brightness structure. Using archival HST/ACS images and Gemini/GMOS spectroscopy, we will explore the photometric and spectroscopic properties of these galaxies.

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5.18. Molecular gas in the poststarburst galaxy NGC7331

Symposium - International Astronomical Union ◽

10.1017/s0074180900084801 ◽

1998 ◽

Vol 184 ◽

pp. 247-248

Author(s):

T. Tosaki ◽

Y. Shioya

Keyword(s):

High Resolution ◽

Spiral Galaxy ◽

Stellar Populations ◽

Optical Spectra ◽

Molecular Gas ◽

Early Type ◽

Origin And Evolution ◽

Co Observations

To understand the origin and evolution of starburst activity, we must study the full evolution of starburst; i.e., pre-, on-going, and post-starburst phases. It seems reasonable to suppose the numerous A-type stars indicate past starburst and they show strong Balmer absorption. NGC7331, nearby early-type spiral galaxy, is one of the poststarburst galaxies which show strong Balmer absorption. The optical spectra of NGC7331 were dominated by component of intermediate-age (5 × 109 years) stellar populations (Ohyama & Taniguchi 1996). We present the result of the high resolution CO observations of NGC7331 using Nobeyama Milimeter Array.

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Extragalactic GCs in the near-infrared: genuinely old in E/S0's?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310003017 ◽

2009 ◽

Vol 5 (S262) ◽

pp. 315-316

Author(s):

Ana L. Chies-Santos ◽

Søren S. Larsen

Keyword(s):

Globular Cluster ◽

Stellar Population ◽

Near Infrared ◽

Local Group ◽

Stellar Populations ◽

Age Dating ◽

Early Type ◽

Optical Photometry ◽

Star Forming ◽

Optical Images

Globular cluster (GC) systems are powerful probes to study the evolutionary histories of galaxies, being tracers of major star fomation episodes (Brodie & Strader 2006). They are found around all major galaxies and are easy to see far beyond the local group. Age dating GCs therefore helps pinpoint epochs of major star forming events. Spectroscopic age dating though (Strader et al. 2005) is extremely time consuming and can only access the few brightest clusters. An alternative is to combine near-infrared (NIR) and optical photometry, and therefore have a better chance in lifting the age metallicity degeneracy than with optical colours alone. This approach relies in testing GC colours against simple stellar population (SSP) models. The first studies following this technique showed the possible existence of a high percentage of intermediate age (2-3 Gyrs) GCs in early-type galaxies known to contain old stellar populations from integrated light studies. Two strong cases can be listed: NGC 4365 (Puzia et al. 2002, Larsen et al. 2005) and NGC 5846 (Hempel et al. 2003). In the present study we combine NIR deep photometry obtained with the WHT/LIRIS instrument and archival HST/ACS optical images to determine g(F475W), z(F840LP) and K(2.2m) magnitudes and colours of GCs in 14 early-type galaxies.

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Spatially Resolved Stellar Populations and Kinematics with KCWI: Probing the Assembly History of the Massive Early-type Galaxy NGC 1407

The Astrophysical Journal ◽

10.3847/1538-4357/ab2126 ◽

2019 ◽

Vol 878 (2) ◽

pp. 129 ◽

Cited By ~ 2

Author(s):

Anna Ferré-Mateu ◽

Duncan A. Forbes ◽

Richard M. McDermid ◽

Aaron J. Romanowsky ◽

Jean P. Brodie

Keyword(s):

Stellar Populations ◽

Early Type ◽

Spatially Resolved ◽

History Of ◽

Early Type Galaxy

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Mid Infrared Colors of Early Type Galaxies

The Evolution of Galaxies ◽

10.1007/978-94-017-3313-7_55 ◽

2001 ◽

pp. 251-254

Author(s):

Alessandro Bressan ◽

Hervé Aussel ◽

Gian Luigi Granato ◽

Giulia Rodighiero ◽

Pasquale Panuzzo ◽

...

Keyword(s):

Early Type ◽

Mid Infrared

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Extremely α‐Enriched Globular Clusters in Early‐Type Galaxies: A Step toward the Dawn of Stellar Populations?

The Astrophysical Journal ◽

10.1086/505679 ◽

2006 ◽

Vol 648 (1) ◽

pp. 383-388 ◽

Cited By ~ 31

Author(s):

Thomas H. Puzia ◽

Markus Kissler‐Patig ◽

Paul Goudfrooij

Keyword(s):

Globular Clusters ◽

Stellar Populations ◽

Early Type

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The quest for relics: Massive compact galaxies in the local Universe

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009505 ◽

2019 ◽

Vol 15 (S352) ◽

pp. 320-321

Author(s):

A. Schnorr-Müller ◽

M. Trevisan ◽

F. S. Lohmann ◽

N. Mallmann ◽

R. Riffel ◽

...

Keyword(s):

Matched Control ◽

High Redshift ◽

Control Sample ◽

Stellar Populations ◽

Velocity Fields ◽

Current Data ◽

Early Type ◽

Local Universe ◽

Compact Galaxies

AbstractIn the local Universe there exists a rare population of compact galaxies resembling the high-redshift quiescent population in mass and size. It has been found that some of these objects have survived largely unchanged since their formation at high-z. They are called relic galaxies. With the goal of finding relic galaxies, we searched the SDSS-MaNGA DR15 release for massive compact galaxies. We find that massive compact galaxies are mostly composed of old, metal-rich and alpha enhanced stellar populations. In terms of kinematics, massive compact galaxies show ordered rotation in their velocity fields and σ* profiles rising towards the center. They are predominantly fast rotators and show increased rotational support when compared to a mass-matched control sample of average-sized early-type galaxies. These properties are consistent with these objects being relic galaxies. However, to confirm their relic status, we need to probe larger radii (⪎3Re) than probed with the current data.

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