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

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.

scholarly journals The evolution of galaxy sizes

2012 ◽  
Vol 8 (S295) ◽  
pp. 151-154 ◽  
Author(s):  
Bianca M. Poggianti ◽  
Rosa Calvi ◽  
Daniele Bindoni ◽  
Mauro D'Onofrio ◽  
Alessia Moretti ◽  
...  
Keyword(s):  
Stellar Populations ◽  
Early Type ◽  
Average Amount ◽  
Local Universe ◽  
Size Evolution ◽  
General Field ◽  
Compact Galaxies ◽  
Galaxy Environment ◽  
Stellar Masses ◽  
Individual Galaxies

AbstractWe present a study of galaxy sizes in the local Universe as a function of galaxy environment, comparing clusters and the general field. Galaxies with radii and masses comparable to high-z massive and compact galaxies represent 4.4% of all galaxies more massive than 3 × 1010M⊙ in the field. Such galaxies are 3 times more frequent in clusters than in the field. Most of them are early-type galaxies with intermediate to old stellar populations. There is a trend of smaller radii for older luminosity-weighted ages at fixed galaxy mass. We show the relation between size and luminosity-weighted age for galaxies of different stellar masses and in different environments. We compare with high-z data to quantify the evolution of galaxy sizes. We find that, once the progenitor bias due to the relation between galaxy size and stellar age is removed, the average amount of size evolution of individual galaxies between high- and low-z is mild, of the order of a factor 1.6.

The Quest for Relics: Massive compact galaxies in the local Universe

2019 ◽  
Vol 15 (S359) ◽  
pp. 441-443
Author(s):  
F. S. Lohmann ◽  
A. Schnorr-Müller ◽  
M. Trevisan ◽  
R. Riffel ◽  
N. Mallmann ◽  
...  
Keyword(s):  
High Redshift ◽  
Control Sample ◽  
Sloan Digital Sky Survey ◽  
Integral Field Spectroscopy ◽  
Sky Survey ◽  
Size Evolution ◽  
Compact Galaxies ◽  
Minor Mergers ◽  
Significant Size ◽  
Integral Field

AbstractObservations at high redshift reveal that a population of massive, quiescent galaxies (called red nuggets) already existed 10 Gyr ago. These objects undergo a significant size evolution over time, likely due to minor mergers. In this work we present an analysis of local massive compact galaxies to assess if their properties are consistent with what is expected for unevolved red nuggets (relic galaxies). Using integral field spectroscopy (IFS) data from the MaNGA survey from the Sloan Digital Sky Survey (SDSS), we characterized the kinematics and properties of stellar populations of massive compact galaxies, and find that these objects exhibit, on average, a higher rotational support than a control sample of average sized early-type galaxies. This is in agreement with a scenario in which these objects have a quiet accretion history, rendering them candidates for relic galaxies.

scholarly journals Dissecting the Formation Histories of Galaxies with Stellar Populations Models

2009 ◽  
Vol 5 (S262) ◽  
pp. 153-163
Author(s):  
Ivo Labbé
Keyword(s):  
Star Formation ◽  
Current Knowledge ◽  
High Redshift ◽  
Local Environment ◽  
Stellar Populations ◽  
Current Data ◽  
Star Formation History ◽  
Spectral Energy ◽  
Formation History ◽  
History Of

AbstractHow did galaxies evolve from primordial fluctuations to the well-ordered but diverse population of disk and elliptical galaxies that we observe today? Stellar populations synthesis models have become a crucial tool in addressing this question by helping us to interpret the spectral energy distributions of present-day galaxies and their high redshift progenitors in terms of fundamental characteristics such as stellar mass and age. I will review our current knowledge on the evolution of stellar populations in early- and late type galaxies at z < 1 and the tantalizing – but incomplete – view of the stellar populations in galaxies at 1 < z < 3, during the global peak of star formation. Despite great progress, many fundamental questions remain: what processes trigger episodes of galaxy-scale star formation and what quenches them? To what degree does the star formation history of galaxies depend on the merger history, (halo) mass, or local environment? I will discuss some of the challenges posed in interpreting current data and what improved results might be expected from new observational facilities in the near- and more distant future.

scholarly journals Characterization of peculiar early-type galaxies in the local universe

2012 ◽  
Vol 10 (H16) ◽  
pp. 333-333
Author(s):  
Beatriz H. F. Ramos ◽  
Karín Menéndez-Delmestre ◽  
Taehyun Kim ◽  
Kartik Sheth ◽  
Keyword(s):  
Star Formation ◽  
Broad Band ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Stellar Structure ◽  
Host Galaxy ◽  
Early Type ◽  
Local Universe ◽  
The Galaxy ◽  
Stellar Masses

AbstractEarly-type galaxies (ETGs) have been characterized as objects dominated by old stellar populations, containing little or no cold gas and dust, and thus, non-existent star formation. However, there are indications in the literature that some ETGs deviate from this: some have significant amounts of gas and dust, are forming stars, and/or display stellar substructures (tidal features, disks or shells, e.g., Kormendy et al. 1997, Rix, Carollo & Freeman 1999). A better understanding of the evolution of ETGs and the details of their “peculiarities” is critical to properly constrain models of galaxy formation. We present preliminary results on a photometric analysis of substructures in local ETGs, based on 3.6μm IRAC images from the Spitzer Survey of Stellar Structure in Galaxies (S4G; Sheth et al. 2010), which comprises one of the largest mid-IR photometric surveys of the local Universe. Relatively unhindered by extinction and dominated by the low-mass stellar populations that dominate a galaxy's stellar mass budget, the IR is the ideal waveband to trace the details of stellar structures in galaxies. Based on 2D GALFIT (Peng et al. 2002) decomposition, we find tidal features in 17% of 146 ETGs from S4G. For both the GALFIT model and the galaxy residual images, we calculate the total counts inside an annular region centered on the galaxy, where the inner radius is the effective radius of the galaxy. Assuming that a tidal feature and its host galaxy have the same mass-to-luminosity ratio (M/L), the ratio of the residual counts over model counts translates into the ratio of their stellar masses. We find that the tidal features in the majority of peculiar ETGs in our sample account for no more than 11% of the galaxy's total stellar mass. Considering that simulations (Canalizo et al. 2007) suggest an upper limit in relative stellar mass of 25% for shells resulting from a past major merger, the values we find support a merger origin. We are in the process of applying the decomposition method to GALEX UV images and optical SDSS images of these peculiar ETGs in order to characterize the underlying substructure and provide constraints on astrophysical properties such as star formation rates and stellar masses associated to these tidal features, based on broad-band SED template fitting techniques.

scholarly journals The MOSDEF survey: differences in SFR and metallicity for morphologically selected mergers at z ∼ 2

2020 ◽  
Vol 501 (1) ◽  
pp. 137-145
Author(s):  
Katelyn Horstman ◽  
Alice E Shapley ◽  
Ryan L Sanders ◽  
Bahram Mobasher ◽  
Naveen A Reddy ◽  
...  
Keyword(s):  
High Redshift ◽  
Statistical Significance ◽  
Formation Rate ◽  
Control Sample ◽  
Stellar Mass ◽  
Mass Star ◽  
Local Universe ◽  
Galaxy Interactions ◽  
Isolated Galaxies ◽  
Future Work

ABSTRACT We study the properties of 55 morphologically-identified merging galaxy systems at z ∼ 2. These systems are flagged as mergers based on features such as tidal tails, double nuclei, and asymmetry. Our sample is drawn from the MOSFIRE Deep Evolution Field (MOSDEF) survey, along with a control sample of isolated galaxies at the same redshift. We consider the relationships between stellar mass, star formation rate (SFR), and gas-phase metallicity for both merging and non-merging systems. In the local universe, merging systems are characterized by an elevated SFR and depressed metallicity compared to isolated systems at a given mass. Our results indicate SFR enhancement and metallicity deficit for merging systems relative to non-merging systems for a fixed stellar mass at z ∼ 2, though larger samples are required to establish these preliminary results with higher statistical significance. In future work, it will be important to establish if the enhanced SFR and depressed metallicity in high-redshift mergers deviate from the ‘fundamental metallicity relation,’ as is observed in mergers in the local universe, and therefore shed light on gas flows during galaxy interactions.

The IMF-SFH connection in massive early-type galaxies

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
I. Ferreras ◽  
C. Weidner ◽  
A. Vazdekis ◽  
F. La Barbera
Keyword(s):  
Age Distribution ◽  
Stellar Populations ◽  
Mass Function ◽  
Initial Mass Function ◽  
Population Synthesis ◽  
Early Type ◽  
Massive Galaxies ◽  
Stellar Initial Mass Function ◽  
The Many ◽  
The Imf

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.

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

2006 ◽  
Vol 2 (S241) ◽  
Author(s):  
A. Bressan ◽  
P. Panuzzo ◽  
O. Vega ◽  
L. Buson ◽  
M. Clemens ◽  
...  
Keyword(s):  
Stellar Populations ◽  
Early Type ◽  
Mid Infrared

scholarly journals Star formation histories of resolved galaxies

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.

scholarly journals Stellar Populations of the Most Massive Galaxies

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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