scholarly journals Compact, bulge dominated structures of spectroscopically confirmed quiescent galaxies at z ≈ 3

2020 ◽  
Author(s):  
Peter Lustig ◽  
Veronica Strazzullo ◽  
Chiara D’Eugenio ◽  
Emanuele Daddi ◽  
Maurilio Pannella ◽  
...  
Keyword(s):  
Structural Properties ◽  
Surface Brightness ◽  
Cosmic Time ◽  
Stellar Populations ◽  
Statistical Estimates ◽  
The Galaxy ◽  
Mass Size ◽  
Formation And Evolution ◽  
Size Relation ◽  
Good Agreement

Abstract We study structural properties of spectroscopically confirmed massive quiescent galaxies at z ≈ 3 with one of the first sizeable samples of such sources, made of ten 10.8 < log (M⋆/M⊙) < 11.3 galaxies at 2.4 < z < 3.2 in the COSMOS field whose redshifts and quiescence are confirmed by HST grism spectroscopy. Although affected by a weak bias toward younger stellar populations, this sample is deemed to be largely representative of the majority of the most massive and thus intrinsically rarest quiescent sources at this cosmic time. We rely on targeted HST/WFC3 observations and fit Sérsic profiles to the galaxy surface brightness distributions at ≈4000Årestframe. We find typically high Sérsic indices and axis ratios (medians ≈4.5 and 0.73, respectively) suggesting that, at odds with some previous results, the first massive quiescent galaxies may largely be already bulge-dominated systems. We measure compact galaxy sizes with an average of ≈1.4kpc at log (M⋆/M⊙) ≈ 11.2, in good agreement with the extrapolation at the highest masses of previous determinations of the stellar mass - size relation of quiescent galaxies, and of its redshift evolution, from photometrically selected samples at lower and similar redshifts. This work confirms the existence of a population of compact, bulge dominated, massive, quiescent sources at z ≈ 3, providing one of the first statistical estimates of their structural properties, and further constraining the early formation and evolution of the first quiescent galaxies.

scholarly journals Properties of extragalactic thick discs recovered from ultra-deep Stripe82 imaging

2019 ◽  
Vol 629 ◽  
pp. A12 ◽  
Author(s):  
C. Martínez-Lombilla ◽  
J. H. Knapen
Keyword(s):  
Surface Brightness ◽  
Vertical Surface ◽  
Thick Disc ◽  
Deep Imaging ◽  
Low Surface Brightness ◽  
The Galaxy ◽  
History Of ◽  
Formation And Evolution ◽  
Disc Galaxies ◽  
Good Agreement

Context. Thick discs can give invaluable information on the formation and evolution history of galaxies as most, if not all, disc galaxies have a thin (classical) disc and a thick disc. Aims. We study the structure of thick discs in extraordinary depth by reaching a surface brightness limit of μrdeep ∼ 28.5−29 mag arcsec−2 with combined g, r, i band images from the IAC Stripe 82 Legacy Project. Methods. We present the characterisation of the thick discs in a sample of five edge-on galaxies. A study of the radial and vertical surface brightness profiles is presented by comparing our data with point spread function (PSF) deconvolved models. Our method begins with an analysis of the background and masking processes. Then we consider the effects of the PSF through galaxy modelling. The galaxy disc components are fitted considering that the thin and thick discs are two stellar fluids that are gravitationally coupled in hydrostatic equilibrium. Results. We find that effects due to the PSF are significant when low surface brightness is reached, especially in the vertical profiles, but it can be accounted for by careful modelling. The galaxy outskirts are strongly affected by the faint wings of the PSF, mainly by PSF-redistributed light from the thin disc. This is a central problem for ultra-deep imaging. The thick-disc component is required to reach satisfactory fit results in the more complex galaxies in our sample, although it is not required for all galaxies. When the PSF is ignored, the brightness of these structures may be overestimated by up to a factor of ∼4. Conclusions. In general, our results are in good agreement with those of previous works, although we reach deeper surface brightness levels, so that the PSF effects are stronger. We obtain scale heights and mass ratios of thin and thick discs (zt, zT, and MT/Mt), which provide excellent agreement with previous studies. Our small initial sample provides evidence for aspects of a wide variety of formation theories for the thick discs in disc galaxies.

GALAXY EVOLUTION THROUGH THE COSMIC TIME

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1371-1377
Author(s):  
T. P. IDIART ◽  
J. A. F. PACHECO ◽  
J. SILK
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Cosmic Time ◽  
Evolutionary Model ◽  
Stellar Populations ◽  
Elliptical Galaxies ◽  
Star Formation Activity ◽  
Formation And Evolution ◽  
The Universe

Elliptical galaxies are the best systems to study the early star formation activity in the universe. This work aims to understand the formation and evolution of these objects through the study of the integrated properties of their stellar populations. Here an evolutionary model is developed and their predicted spectrophotometric properties are presented.

scholarly journals An interesting case of the formation and evolution of a barred galaxy in the cosmological context

2020 ◽  
Vol 642 ◽  
pp. L12
Author(s):  
Ewa L. Łokas
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cosmic Time ◽  
Galaxy Cluster ◽  
Interesting Case ◽  
Massive Galaxies ◽  
Barred Galaxies ◽  
Tidal Interactions ◽  
The Galaxy ◽  
Formation And Evolution

Elongated, bar-like galaxies without a significant disk component, with little rotation support and no gas, often form as a result of tidal interactions with a galaxy cluster, as was recently demonstrated using the IllustrisTNG-100 simulation. Galaxies that exhibit similar properties are, however, also found to be infalling into the cluster for the first time. We use the same simulation to study in detail the history of such a galaxy over cosmic time in order to determine its origin. The bar appears to be triggered at t = 6.8 Gyr by the combined effect of the last significant merger with a subhalo and the first passage of another dwarf satellite, both ten times less massive than the galaxy. The satellites deposit all their gas in the galaxy, contributing to its third and last star-formation episode, which perturbs the disk and may also contribute to the formation of the bar. The galaxy then starts to lose its gas and dark matter due to its passage near a group of more massive galaxies. The strongest interaction involves a galaxy 22 times more massive, leaving the barred galaxy with no gas and half of its maximum dark matter mass. During this time, the bar grows steadily, seemingly unaffected by the interactions, although they may have aided its growth by stripping the gas. The studied galaxy, together with two other similar objects briefly discussed in this Letter, suggest the existence of a new class of early-type barred galaxies and thereby demonstrate the importance of interactions in galaxy formation and evolution.

scholarly journals New Observational Clues on Binary Formation in the Galaxy

1989 ◽  
Vol 8 ◽  
pp. 103-107
Author(s):  
David W. Latham
Keyword(s):  
Strong Dependence ◽  
Stellar Populations ◽  
Close Binaries ◽  
Major Influence ◽  
Solar Mass ◽  
Multiple Systems ◽  
Binary Formation ◽  
The Galaxy ◽  
Low Mass ◽  
Formation And Evolution

AbstractNew observations of binaries are beginning to provide new clues on the formation and evolution of binary and multiple systems in a variety of stellar populations in the Galaxy. New orbital determinations are shedding light on the frequency and orbital characteristics of binaries in the disk and the halo of our Galaxy, both in clusters and the field. These results support the view that the formation of binaries involving solar-mass stars is relatively independent of the stellar environment. Evolutionary effects can have a major influence for close binaries with periods up to at least ten days, with a strong dependence on the age of the population. Progress towards determining the frequency of low-mass companions and planetary systems is promising but still very limited.

Disk Galaxies in the Magneticum Pathfinder Simulations

2014 ◽  
Vol 10 (S309) ◽  
pp. 145-148 ◽  
Author(s):  
Rhea-Silvia Remus ◽  
Klaus Dolag ◽  
Lisa K. Bachmann ◽  
Alexander M. Beck ◽  
Andreas Burkert ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Mass Function ◽  
Disk Galaxies ◽  
Physical Processes ◽  
Galaxy Formation And Evolution ◽  
Mass Size ◽  
Formation And Evolution ◽  
Galaxy Populations ◽  
Size Relation ◽  
The Universe

AbstractWe presentMagneticum Pathfinder, a new set of hydrodynamical cosmological simulations covering a large range of cosmological scales. Among the important physical processes included in the simulations are the chemical and thermodynamical evolution of the diffuse gas as well as the evolution of stars and black holes and the corresponding feedback channels. In the high resolution boxes aimed at studies of galaxy formation and evolution, populations of both disk and spheroidal galaxies are self-consistently reproduced. These galaxy populations match the observed stellar mass function and show the same trends for disks and spheroids in the mass–size relation as observations from the SDSS. Additionally, we demonstrate that the simulated galaxies successfully reproduce the observed specific angular-momentum–mass relations for the two different morphological types of galaxies. In summary, theMagneticum Pathfindersimulations are a valuable tool for studying the assembly of cosmic and galactic structures in the universe.

scholarly journals What is the physics behind the Larson mass–size relation?

2019 ◽  
Vol 490 (2) ◽  
pp. 2648-2655 ◽  
Author(s):  
J Ballesteros-Paredes ◽  
C Román-Zúñiga ◽  
Q Salomé ◽  
M Zamora-Avilés ◽  
M J Jiménez-Donaire
Keyword(s):  
Power Law ◽  
Molecular Clouds ◽  
Line Of Sight ◽  
Random Factor ◽  
Dense Cores ◽  
The Galaxy ◽  
Mass Size ◽  
Gas Contamination ◽  
Theoretical Evidence ◽  
Size Relation

ABSTRACT Different studies have reported a power-law mass–size relation M ∝ Rq for ensembles of molecular clouds. In the case of nearby clouds, the index of the power-law q is close to 2. However, for clouds spread all over the Galaxy, indexes larger than 2 are reported. We show that indexes larger than 2 could be the result of line-of-sight superposition of emission that does not belong to the cloud itself. We found that a random factor of gas contamination, between 0.001 per cent and 10 per cent of the line of sight, allows to reproduce the mass–size relation with q ∼ 2.2–2.3 observed in Galactic CO surveys. Furthermore, for dense cores within a single cloud, or molecular clouds within a single galaxy, we argue that, even in these cases, there is observational and theoretical evidence that some degree of superposition may be occurring. However, additional effects may be present in each case, and are briefly discussed. We also argue that defining the fractal dimension of clouds via the mass–size relation is not adequate, since the mass is not necessarily a proxy to the area, and the size reported in M−R relations is typically obtained from the square root of the area, rather than from an estimation of the size independent from the area. Finally, we argue that the statistical analysis of finding clouds satisfying the Larson’s relations does not mean that each individual cloud is in virial equilibrium.

scholarly journals Stellar populations in the outskirts of M31: the mid-infrared view

2016 ◽  
Vol 11 (S321) ◽  
pp. 19-21
Author(s):  
P. Barmby ◽  
M. Rafiei Ravandi
Keyword(s):  
Point Source ◽  
Surface Brightness ◽  
Cross Correlation ◽  
Stellar Populations ◽  
Low Mass Stars ◽  
Mid Infrared ◽  
Star Count ◽  
The Galaxy ◽  
Low Mass ◽  
Point Source Catalog

AbstractThe mid-infrared provides a unique view of galaxy stellar populations, sensitive to both the integrated light of old, low-mass stars and to individual dusty mass-losing stars. We present results from an extended Spitzer/IRAC survey of M31 with total lengths of 6.6 and 4.4 degrees along the major and minor axes, respectively. The integrated surface brightness profile proves to be surprisingly difficult to trace in the outskirts of the galaxy, but we can also investigate the disk/halo transition via a star count profile, with careful correction for foreground and background contamination. Our point-source catalog allows us to report on mid-infrared properties of individual objects in the outskirts of M31, via cross-correlation with PAndAS, WISE, and other catalogs.

scholarly journals Structural analysis of massive galaxies using HST deep imaging at z < 0.5

2020 ◽  
Vol 634 ◽  
pp. A11
Author(s):  
Sandra N. dos Reis ◽  
Fernando Buitrago ◽  
Polychronis Papaderos ◽  
Israel Matute ◽  
José Afonso ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Structural Parameters ◽  
Structural Evolution ◽  
Morphological Type ◽  
Formation Mechanisms ◽  
Massive Galaxies ◽  
Local Mass ◽  
Mass Size ◽  
Mass Assembly ◽  
Size Relation

Context. The most massive galaxies (Mstellar ≥ 1011 M⊙) in the local Universe are characterized by a bulge-dominated morphology and old stellar populations, in addition to being confined to a tight mass-size relation. Identifying their main components can provide insights into their formation mechanisms and subsequent mass assembly. Aims. Taking advantage of Hubble Space Telescope (HST) CANDELS data, we analyze the lowest redshift (z <  0.5) massive galaxies in the H and I band in order to disentangle their structural constituents and study possible faint non-axisymmetric features. Methods. Our final sample consists of 17 massive galaxies. Due to the excellent HST spatial resolution for intermediate redshift objects, they are hard to model by purely automatic parametric fitting algorithms. We performed careful single and double (bulge-disk decompositions) Sérsic fits to their galaxy surface brightness profiles. We compare the model color profiles with the observed ones and also derive multi-component global effective radii attempting to obtain a better interpretation of the mass-size relation. Additionally, we test the robustness of our measured structural parameters via simulations. Results. We find that the Sérsic index does not offer a good proxy for the visual morphological type for our sample of massive galaxies. Our derived multi-component effective radii give a better description of the size of our sample galaxies than those inferred from single Sérsic models with GALFIT. Our galaxy population lies on the scatter of the local mass-size relation, indicating that these massive galaxies have not experienced a significant growth in size since z ∼ 0.5. Interestingly, the few outliers are late-type galaxies, indicating that spheroids must reach the local mass-size relation earlier. For most of our sample galaxies, both single- and multi-component Sérsic models with GALFIT show substantial systematic deviations from the observed surface brightness profiles in the outskirts. These residuals may be partly due to several factors, namely a nonoptimal data reduction for low surface brightness features or the existence of prominent stellar haloes for massive galaxies, or they could also arise from conceptual shortcomings of parametric 2D image decomposition tools. They consequently propagate into galaxy color profiles. This is a significant obstacle to the exploration of the structural evolution of galaxies, which calls for a critical assessment and refinement of existing surface photometry techniques.

scholarly journals HST/WFC3 grism observations of z ∼ 1 clusters: evidence for evolution in the mass–size relation of quiescent galaxies from post-starburst galaxies

2020 ◽  
Vol 493 (4) ◽  
pp. 6011-6032 ◽  
Author(s):  
J Matharu ◽  
A Muzzin ◽  
G B Brammer ◽  
R F J van der Burg ◽  
M W Auger ◽  
...  
Keyword(s):  
Rapid Change ◽  
Driving Mechanism ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Large Size ◽  
The Galaxy ◽  
Size Growth ◽  
Mass Size ◽  
Minor Mergers ◽  
Size Relation

ABSTRACT Minor mergers have been proposed as the driving mechanism for the size growth of quiescent galaxies with decreasing redshift. The process whereby large star-forming galaxies quench and join the quiescent population at the large size end has also been suggested as an explanation for this size growth. Given the clear association of quenching with clusters, we explore this mechanism by studying the structural properties of 23 spectroscopically identified recently quenched (or ‘post-starburst’ (PSB)) cluster galaxies at z ∼ 1. Despite clear PSB spectral signatures implying rapid and violent quenching, 87 per cent of these galaxies have symmetric, undisturbed morphologies in the stellar continuum. Remarkably, they follow a mass–size relation lying midway between the star-forming and quiescent field relations, with sizes 0.1 dex smaller than z ∼ 1 star-forming galaxies at log(M*/M⊙) = 10.5. This implies a rapid change in the light profile without directly effecting the stellar distribution, suggesting changes in the mass-to-light ratio gradients across the galaxy are responsible. We develop fading toy models to explore how star-forming galaxies move across the mass–size plane as their stellar populations fade to match those of the PSBs. ‘Outside-in’ fading has the potential to reproduce the contraction in size and increase in bulge-dominance observed between star-forming and PSB cluster galaxies. Since cluster PSBs lie on the large size end of the quiescent mass–size relation, and our previous work shows cluster galaxies are smaller than field galaxies, the sizes of quiescent galaxies must grow both from the quenching of star-forming galaxies and dry minor mergers.

scholarly journals Atomic and molecular gas in IllustrisTNG galaxies at low redshift

2019 ◽  
Vol 487 (2) ◽  
pp. 1529-1550 ◽  
Author(s):  
Benedikt Diemer ◽  
Adam R H Stevens ◽  
Claudia del P Lagos ◽  
A R Calette ◽  
Sandro Tacchella ◽  
...  
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Gas Content ◽  
Neutral Gas ◽  
Mass Size ◽  
Mass Functions ◽  
Gas Fractions ◽  
Size Relation ◽  
Good Agreement

ABSTRACT We have recently developed a post-processing framework to estimate the abundance of atomic and molecular hydrogen (H i and H2, respectively) in galaxies in large-volume cosmological simulations. Here we compare the H i and H2 content of IllustrisTNG galaxies to observations. We mostly restrict this comparison to z ≈ 0 and consider six observational metrics: the overall abundance of H i and H2, their mass functions, gas fractions as a function of stellar mass, the correlation between H2 and star formation rate, the spatial distribution of gas, and the correlation between gas content and morphology. We find generally good agreement between simulations and observations, particularly for the gas fractions and the H i mass–size relation. The H2 mass correlates with star formation rate as expected, revealing an almost constant depletion time that evolves up to z = 2 as observed. However, we also discover a number of tensions with varying degrees of significance, including an overestimate of the total neutral gas abundance at z = 0 by about a factor of 2 and a possible excess of satellites with no or very little neutral gas. These conclusions are robust to the modelling of the H i/H2 transition. In terms of their neutral gas properties, the IllustrisTNG simulations represent an enormous improvement over the original Illustris run. All data used in this paper are publicly available as part of the IllustrisTNG data release.

Sign in / Sign up

Export Citation Format

Share Document