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 The structural properties of classical bulges and discs from z ∼ 2

2019 ◽  
Vol 489 (3) ◽  
pp. 4135-4154 ◽  
Author(s):  
Paola Dimauro ◽  
Marc Huertas-Company ◽  
Emanuele Daddi ◽  
Pablo G Pérez-González ◽  
Mariangela Bernardi ◽  
...  
Keyword(s):  
Structural Properties ◽  
Formation Mechanisms ◽  
Massive Galaxies ◽  
Star Forming ◽  
Star Formation Activity ◽  
Mass Size ◽  
Best Fitting ◽  
The One ◽  
Bulge Formation ◽  
Size Relation

ABSTRACT We study the rest-frame optical mass–size relation of bulges and discs from z ∼ 2 to z ∼ 0 for a complete sample of massive galaxies in the CANDELS fields using two-component Sérsic models. Discs and star-forming galaxies follow similar mass–size relations. The mass–size relation of bulges is less steep than the one of quiescent galaxies (best-fitting slope of 0.7 for quiescent galaxies against 0.4 for bulges). We find little dependence of the structural properties of massive bulges and discs with the global morphology of galaxies (disc versus bulge dominated) and the star formation activity (star-forming versus quiescent). This result suggests similar bulge formation mechanisms for most massive galaxies and also that the formation of the bulge component does not significantly affect the disc structure. Our results pose a challenge to current cosmological models that predict distinct structural properties for stellar bulges arising from mergers and disc instabilities.

scholarly journals Truncated disc surface brightness profiles produced by flares

2016 ◽  
Vol 11 (S321) ◽  
pp. 272-272
Author(s):  
Alejandro Borlaff ◽  
M. Carmen Eliche-Moral ◽  
John Beckman ◽  
Joan Font
Keyword(s):  
Surface Brightness ◽  
Structural Parameters ◽  
Morphological Type ◽  
Hubble Sequence ◽  
Wide Range ◽  
The Face ◽  
Analogous Model ◽  
Galaxy Model ◽  
Realistic Images ◽  
Real Type

AbstractPrevious studies have discarded that flares in galactic discs may explain the truncation that are frequently observed in highly-inclined galaxies (Kregel et al. 2002). However, no study has systematically analysed this hypothesis using realistic models for the disc, the flare and the bulge. We derive edge-on and face-on surface brightness profiles for a series of realistic galaxy models with flared discs that sample a wide range of structural and photometric parameters across the Hubble Sequence, accordingly to observations. The surface brightness profile for each galaxy model has been simulated for edge-on and face-on views to find out whether the flared disc produces a significant truncation in the disc in the edge-on view compared to the face-on view or not. In order to simulate realistic images of disc galaxies, we have considered the observational distribution of the photometric parameters as a function of the morphological type for three mass bins (10 < log10(M/M⊙) < 10.7, 10.7 < log10(M/M⊙) < 11 and log10(M/M⊙) > 11), and four morphological type bins (S0–Sa, Sb–Sbc, Sc–Scd and Sd–Sdm). For each mass bin, we have restricted the photometric and structural parameters of each modelled galaxy to their characteristic observational ranges (μ0, disc, μeff, bulge, B/T, Mabs, reff, nbulge, hR, disc) and the flare in the disc (hz, disc/hR, disc, ∂hz, disc/∂R, see de Grijs & Peletier 1997, Graham 2001, López-Corredoira et al. 2002, Yoachim & Dalcanton 2006, Bizyaev et al. 2014, Mosenkov et al. 2015).Contrary to previous claims, the simulations show that realistic flared disks can be responsible for the truncations observed in many edge-on systems, preserving the profile of the non-flared analogous model in face-on view. These breaks reproduce the properties of the weak-to-intermediate breaks observed in many real Type-II galaxies in the diagram relating the radial location of the break (RbrkII) in units of the inner disk scale-length with the break strength S (Laine et al. 2014). Radial variation of the scale-height of the disc (flaring) can explain the existence of many breaks in edge-on galaxies, especially of those with low break strengths $S=\log _{10}\frac{h_{o}}{h_{i}} \sim \ [-0.3,-0.1]$.

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 &lt; log (M⋆/M⊙) &lt; 11.3 galaxies at 2.4 &lt; z &lt; 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 The Fornax Deep Survey with the VST

2019 ◽  
Vol 628 ◽  
pp. A4 ◽  
Author(s):  
M. A. Raj ◽  
E. Iodice ◽  
N. R. Napolitano ◽  
M. Spavone ◽  
H-S. Su ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Structural Parameters ◽  
Absolute Magnitude ◽  
Morphological Type ◽  
High Density ◽  
Molecular Gas ◽  
Type Ii ◽  
Type Iii ◽  
Deep Survey ◽  
Fornax Cluster

Context. We present the study of a magnitude limited sample (mB ≤ 16.6 mag) of 13 late type galaxies (LTGs), observed inside the virial radius, Rvir ∼ 0.7 Mpc, of the Fornax cluster within the Fornax Deep Survey (FDS). Aims. The main objective is to use surface brightness profiles and g − i colour maps to obtain information on the internal structure of these galaxies and find signatures of the mechanisms that drive their evolution in high-density environments inside the virial radius of the cluster. Methods. By modelling galaxy isophotes, we extract the azimuthally averaged surface brightness profiles in four optical bands. We also derive g − i colour profiles, and relevant structural parameters like total magnitude and effective radius. For ten of the galaxies in this sample, we observe a clear discontinuity in their typical exponential surface brightness profiles, derive their “break radius”, and classify their disc-breaks into Type II (down-bending) or Type III (up-bending). Results. We find that Type II galaxies have bluer average (g − i) colour in their outer discs while Type III galaxies are redder. The break radius increases with stellar mass and molecular gas mass while it decreases with molecular gas-fractions. The inner and outer scale-lengths increase monotonically with absolute magnitude, as found in other works. For galaxies with CO(1-0) measurements, there is no detected cold gas beyond the break radius (within the uncertainties). In the context of morphological segregation of LTGs in clusters, we also find that, in Fornax, galaxies with morphological type 5 <  T ≤ 9 (∼60% of the sample) are located beyond the high-density, ETG-dominated regions, however there is no correlation between T and the disc-break type. We do not find any correlation between the average (g − i) colours and cluster-centric distance, but the colour-magnitude relation holds true. Conclusions. The main results of this work suggest that the disc-breaks of LTGs inside the virial radius of the Fornax cluster seem to have arisen through a variety of mechanisms (e.g. ram-pressure stripping, tidal disruption), which is evident in their outer-disc colours and the absence of molecular gas beyond their break radius in some cases. This can result in a variety of stellar populations inside and outside the break radii.

Structural evolution of massive early-type galaxies

2012 ◽  
Vol 8 (S295) ◽  
pp. 204-207
Author(s):  
Ludwig Oser ◽  
Thorsten Naab ◽  
Jeremiah P. Ostriker ◽  
Peter H. Johansson
Keyword(s):  
Structural Evolution ◽  
Central Line ◽  
Dominant Mode ◽  
Strong Increase ◽  
Massive Galaxies ◽  
Stellar Velocity ◽  
Mass Size ◽  
Velocity Dispersions ◽  
Stellar Mergers ◽  
Loss Of Compactness

AbstractWe use a large sample of cosmological re-simulations of individual massive galaxies to investigate the origin of the strong increase in sizes and weak decrease of the stellar velocity dispersions since z = 2. At the end of a rapid early phase of star-formation, where stars are created from infalling cold gas, our simulated galaxies are all compact with projected half-mass radii of ≲ 1 kpc and central line-of-sight velocity dispersions of ≈ 262 km s−1. At lower redshifts (z < 2) those galaxies grow predominantly by the accretion of smaller stellar systems and evolve towards the observed local mass-size and mass-velocity dispersion relations. This loss of compactness is accompanied with an increase of central dark matter fractions. We find that the structural evolution of massive galaxies can be explained by frequent minor stellar mergers, which is the dominant mode of accretion for our simulated galaxies.

scholarly journals Superdense massive galaxies in the nearby universe

2009 ◽  
Vol 5 (S262) ◽  
pp. 331-332
Author(s):  
Anna Ferré-Mateu ◽  
Ignacio Trujillo
Keyword(s):  
Value Added ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Local Universe ◽  
Massive Galaxies ◽  
The Past ◽  
Mass Size ◽  
Size Relation

AbstractAt high-z the most superdense massive galaxies are supposed to be the result of gas-rich mergers resulting in compact remnant (Khochfar & Silk (2006); Naab et al. (2007)). After this, dry mergers are expected to be the mechanism that moves these very massive galaxies towards the current stellar mass size relation. Whitin these merging scenarios, a non-negligible fraction (1-10%) of these galaxies is expected to survive since that epoch retaining their compactness and presenting old stellar populations in the past universe.Using the NYU Value-Added Galaxy Catalog (DR6), we find only a tiny fraction of galaxies (~0.03%) with re ≤ 1.5 kpc and M* ≥ 8x1010M⊙ in the local Universe (z~0.2). Surprisingly, they are relatively young (~2Gyr) and metal rich ([Z/H]~0.2) These results have been published in Trujillo et al. (2009)

scholarly journals A connection between bulge properties and the bimodality of galaxies

2007 ◽  
Vol 3 (S245) ◽  
pp. 67-70
Author(s):  
Niv Drory ◽  
David B. Fisher
Keyword(s):  
Surface Brightness ◽  
Structural Parameters ◽  
Formation Mechanisms ◽  
Disk Galaxies ◽  
Central Surface ◽  
Detailed Surface ◽  
The Galaxy ◽  
Blue Galaxies ◽  
Nearby Galaxies ◽  
Red Galaxies

AbstractThe global colors and structure of galaxies have recently been shown to follow bimodal distributions. Galaxies separate into a “red sequence”, populated prototypically by early-type galaxies, and a “blue cloud”, whose typical objects are late-type disk galaxies. Intermediate-type (Sa-Sbc) galaxies populate both regions. It has been suggested that this bimodality reflects the two-component nature of disk-bulge galaxies. However, it has now been established that there are two types of bulges: “classical bulges” that are dynamically hot systems resembling (little) ellipticals, and “pseudobulges”, dynamically cold, flattened, disk-like structures that could not have formed via violent relaxation. Alas, given the different formation mechanisms of these bulges, the question is whether at types Sa-Sbc, where both bulge types are found, the red-blue dichotomy separates galaxies at some value of disk-to-bulge ratio,B/T, or, whether it separates galaxies of different bulge type, irrespective of theirB/T. In this paper, we identify classical bulges and pseudobulges morphologically with HST images in a sample of nearby galaxies. Detailed surface photometry reveals that: (1) The red – blue dichotomy is a function of bulge type: at the sameB/T, pseudobulges are in globally blue galaxies and classical bulges are in globally red galaxies. (2) Bulge type also predicts where the galaxy lies in other (bimodal) global structural parameters: global Sérsic index and central surface brightness. Hence, the red – blue dichotomy is not due to decreasing bulge prominence alone, and the bulge type of a galaxy carries significance for the galaxy's evolutionary history.

scholarly journals Multiparametric scaling relations for dwarf irregular galaxies in different environments

2012 ◽  
Vol 8 (S289) ◽  
pp. 236-239
Author(s):  
M. E. Sharina ◽  
V. E. Karachentseva ◽  
D. I. Makarov
Keyword(s):  
Small Groups ◽  
Surface Brightness ◽  
Structural Parameters ◽  
Absolute Magnitude ◽  
Rotation Velocity ◽  
Lower Surface ◽  
Morphological Type ◽  
Distance Measurements ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies

AbstractWe study the correlations of rotation velocity and absolute magnitude with surface brightness for low surface brightness dwarf irregular galaxies (dIrrs). We find that isolated objects contribute most to the scatter in the Tully–Fisher relation (TFR). Excluding these extreme cases, we develop a three-parameter (luminosity, Hi line width at 20% of peak flux level, i.e., W20, effective surface brightness) TFR for 60 dIrrs (with revised Hubble type T > 8) in the Local Volume (LV) with Cepheid and tip-of-the-red-giant-branch distance measurements. The relation is applied to galaxies of the same morphological type with radial velocities vLG ≤ 3500 km s−1 in the Local Supercluster. We obtained surface photometry and determined structural parameters using sdss images. The rotational velocities and derived photometric parameters for most galaxies in small groups agree well with those corresponding to the three-parameter TFR. However, isolated galaxies appear to have systematically lower surface brightnesses and longer scale lengths for the same luminosity than galaxies in small groups. This may indicate on average twice larger Hi-to-optical disk size ratios for our sample of isolated dIrrs, because their Hi surface densities calculated using the optical diameters look normal.

scholarly journals The role of mergers and interactions in driving the evolution of dwarf galaxies over cosmic time

2020 ◽  
Vol 500 (4) ◽  
pp. 4937-4957 ◽  
Author(s):  
G Martin ◽  
R A Jackson ◽  
S Kaviraj ◽  
H Choi ◽  
J E G Devriendt ◽  
...  
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
Large Fraction ◽  
Structural Evolution ◽  
Cosmic Time ◽  
Stellar Mass ◽  
High Mass ◽  
Key Drivers ◽  
Mass Assembly

ABSTRACT Dwarf galaxies (M⋆ &lt; 109 M⊙) are key drivers of mass assembly in high-mass galaxies, but relatively little is understood about the assembly of dwarf galaxies themselves. Using the NewHorizon cosmological simulation (∼40 pc spatial resolution), we investigate how mergers and fly-bys drive the mass assembly and structural evolution of around 1000 field and group dwarfs up to z = 0.5. We find that, while dwarf galaxies often exhibit disturbed morphologies (5 and 20 per cent are disturbed at z = 1 and z = 3 respectively), only a small proportion of the morphological disturbances seen in dwarf galaxies are driven by mergers at any redshift (for 109 M⊙, mergers drive under 20 per cent morphological disturbances). They are instead primarily the result of interactions that do not end in a merger (e.g. fly-bys). Given the large fraction of apparently morphologically disturbed dwarf galaxies which are not, in fact, merging, this finding is particularly important to future studies identifying dwarf mergers and post-mergers morphologically at intermediate and high redshifts. Dwarfs typically undergo one major and one minor merger between z = 5 and z = 0.5, accounting for 10 per cent of their total stellar mass. Mergers can also drive moderate star formation enhancements at lower redshifts (3 or 4 times at z = 1), but this accounts for only a few per cent of stellar mass in the dwarf regime given their infrequency. Non-merger interactions drive significantly smaller star formation enhancements (around two times), but their preponderance relative to mergers means they account for around 10 per cent of stellar mass formed in the dwarf regime.

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