scholarly journals The SAMI–Fornax Dwarfs Survey I: sample, observations, and the specific stellar angular momentum of dwarf elliptical galaxies

2020 ◽  
Vol 497 (2) ◽  
pp. 1571-1582 ◽  
Author(s):  
Nicholas Scott ◽  
F Sara Eftekhari ◽  
Reynier F Peletier ◽  
Julia J Bryant ◽  
Joss Bland-Hawthorn ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Stellar Mass ◽  
Formation Mechanisms ◽  
Early Type ◽  
Spatially Resolved ◽  
Galaxy Type ◽  
Stellar Velocity ◽  
Dwarf Elliptical Galaxies ◽  
Low Mass ◽  
Fornax Cluster

ABSTRACT Dwarf ellipticals are the most common galaxy type in cluster environments; however, the challenges associated with their observation mean that their formation mechanisms are still poorly understood. To address this, we present deep integral field observations of a sample of 31 low-mass (107.5 < M⋆ < 109.5 M⊙) early-type galaxies in the Fornax cluster with the SAMI instrument. For 21 galaxies, our observations are sufficiently deep to construct spatially resolved maps of the stellar velocity and velocity dispersion – for the remaining galaxies, we extract global velocities and dispersions from aperture spectra only. From the kinematic maps, we measure the specific stellar angular momentum λR of the lowest mass dE galaxies to date. Combining our observations with early-type galaxy data from the literature spanning a large range in stellar mass, we find that λR decreases towards lower stellar mass, with a corresponding increase in the proportion of slowly rotating galaxies in this regime. The decrease of λR with mass in our sample dE galaxies is consistent with a similar trend seen in somewhat more massive spiral galaxies from the CALIFA survey. This suggests that the degree of dynamical heating required to produce dEs from low-mass starforming progenitors may be relatively modest and consistent with a broad range of formation mechanisms.

scholarly journals Stellar initial mass function variation in massive early-type galaxies: the potential role of the deuterium abundance

2020 ◽  
Vol 498 (3) ◽  
pp. 4051-4059 ◽  
Author(s):  
Timothy A Davis ◽  
Freeke van de Voort
Keyword(s):  
Mass Loss ◽  
Cosmic Time ◽  
Mass Function ◽  
Stellar Mass ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Early Type ◽  
Root Cause ◽  
Stellar Initial Mass Function ◽  
Low Mass

ABSTRACT The observed stellar initial mass function (IMF) appears to vary, becoming bottom-heavy in the centres of the most massive, metal-rich early-type galaxies. It is still unclear what physical processes might cause this IMF variation. In this paper, we demonstrate that the abundance of deuterium in the birth clouds of forming stars may be important in setting the IMF. We use models of disc accretion on to low-mass protostars to show that those forming from deuterium-poor gas are expected to have zero-age main-sequence masses significantly lower than those forming from primordial (high deuterium fraction) material. This deuterium abundance effect depends on stellar mass in our simple models, such that the resulting IMF would become bottom-heavy – as seen in observations. Stellar mass loss is entirely deuterium free and is important in fuelling star formation across cosmic time. Using the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulation we show that stellar mass-loss-induced deuterium variations are strongest in the same regions where IMF variations are observed: at the centres of the most massive, metal-rich, passive galaxies. While our analysis cannot prove that the deuterium abundance is the root cause of the observed IMF variation, it sets the stage for future theoretical and observational attempts to study this possibility.

scholarly journals Stellar angular momentum distribution linked to galaxy morphology

2020 ◽  
Vol 494 (4) ◽  
pp. 5421-5438
Author(s):  
Sarah M Sweet ◽  
Karl Glazebrook ◽  
Danail Obreschkow ◽  
Deanne B Fisher ◽  
Andreas Burkert ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Galaxy Formation ◽  
Initial Distribution ◽  
Dark Matter Halo ◽  
Spatially Resolved ◽  
Stellar Velocity ◽  
Traditional Component ◽  
Field Area ◽  
Integral Field ◽  
High Quality Sample

ABSTRACT We study the spatially resolved stellar specific angular momentum j* in a high-quality sample of 24 Calar Alto Legacy Integral Field Area galaxies covering a broad range of visual morphology, accounting for stellar velocity and velocity dispersion. The shape of the spaxelwise probability density function of normalized s = j*/j*mean, PDF(s), deviates significantly from the near-universal initial distribution expected of baryons in a dark matter halo and can be explained by the expected baryonic effects in galaxy formation that remove and redistribute angular momentum. Further we find that the observed shape of the PDF(s) correlates significantly with photometric morphology, where late-type galaxies have a PDF(s) that is similar to a normal distribution, whereas early types have a strongly skewed PDF(s) resulting from an excess of low-angular momentum material. Galaxies that are known to host pseudo-bulges (bulge Sérsic index nb < 2.2) tend to have less skewed bulge PDF(s), with skewness (b1rb) ≲ 0.8. The PDF(s) encodes both kinematic and photometric information and appears to be a robust tracer of morphology. Its use is motivated by the desire to move away from traditional component-based classifications which are subject to observer bias, to classification on a galaxy’s fundamental (stellar mass and angular momentum) properties. In future, PDF(s) may also be useful as a kinematic decomposition tool.

scholarly journals Early-type galaxy density profiles from IllustrisTNG – I. Galaxy correlations and the impact of baryons

2019 ◽  
Vol 491 (4) ◽  
pp. 5188-5215 ◽  
Author(s):  
Yunchong Wang ◽  
Mark Vogelsberger ◽  
Dandan Xu ◽  
Shude Mao ◽  
Volker Springel ◽  
...  
Keyword(s):  
Dark Matter ◽  
Stellar Mass ◽  
High Mass ◽  
Total Power ◽  
Total Density ◽  
Early Type ◽  
Density Profiles ◽  
Low Mass ◽  
Stellar Masses ◽  
The Impact

ABSTRACT We explore the isothermal total density profiles of early-type galaxies (ETGs) in the IllustrisTNG simulation. For the selected 559 ETGs at z = 0 with stellar masses $10^{10.7}\, \mathrm{M}_{\odot } \leqslant M_{\ast } \leqslant 10^{11.9}\, \mathrm{M}_{\odot }$, the total power-law slope has a mean of 〈γ′〉 = 2.011 ± 0.007 and a scatter of $\sigma _{\gamma ^{\prime }} = 0.171$ over the radial range 0.4–4 times the stellar half-mass radius. Several correlations between γ′ and galactic properties including stellar mass, effective radius, stellar surface density, central velocity dispersion, central dark matter fraction, and in situ-formed stellar mass ratio are compared to observations and other simulations, revealing that IllustrisTNG reproduces many correlation trends, and in particular, γ′ is almost constant with redshift below z = 2. Through analysing IllustrisTNG model variations, we show that black hole kinetic winds are crucial to lowering γ′ and matching observed galaxy correlations. The effects of stellar winds on γ′ are subdominant compared to active galactic nucleus (AGN) feedback, and differ due to the presence of AGN feedback from previous works. The density profiles of the ETG dark matter haloes are well described by steeper than NFW profiles, and they are steeper in the full physics (FP) run than their counterparts in the dark matter-only (DMO) run. Their inner density slopes anticorrelate (remain constant) with the halo mass in the FP (DMO) run, and anticorrelate with the halo concentration parameter c200 in both the types of runs. The dark matter haloes of low-mass ETGs are contracted whereas high-mass ETGs are expanded, suggesting that variations in the total density profile occur through the different halo responses to baryons.

scholarly journals Metallicity gradients in small and nearby spiral galaxies

2019 ◽  
Vol 488 (3) ◽  
pp. 3826-3843 ◽  
Author(s):  
Fabio Bresolin
Keyword(s):  
Galaxy Evolution ◽  
Spiral Galaxies ◽  
Stellar Mass ◽  
H Ii Regions ◽  
Spatially Resolved ◽  
Irregular Galaxies ◽  
Low Mass ◽  
The Mean ◽  
Stellar Masses ◽  
Scale Length

ABSTRACT Spectra of H ii regions obtained with Gemini/GMOS are used to derive the radial metallicity gradients of four small, low-mass spiral galaxies. The analysis of the outer disc of one of them, NGC 1058, uncovers the characteristic flattening found in similar extended disc galaxies. After combining these data with published long-slit observations of nearby spiral galaxies, no evidence for a dependence of the disc scale length-normalized metallicity gradients with stellar mass is found, down to log (M⋆/M⊙) ∼ 8.5. The abundance gradients derived from these observations are compared to predictions from recent cosmological simulations of galaxy evolution, finding that in several cases the simulations fail to reproduce the mean steepening of the gradients, expressed in dex kpc−1, with decreasing stellar mass for present-day galaxies, or do not extend to sufficiently small stellar masses for a meaningful comparison. The mean steepening of the abundance gradients (in dex kpc−1) with decreasing disc scale length is in qualitative agreement with predictions from the inside-out model of Boissier & Prantzos, although the predicted slopes are systematically steeper than observed. This indicates the necessity of including processes such as outflows and radial mixing in similar models of galactic chemical evolution. Published spatially resolved metallicity and photometric data of dwarf irregular galaxies suggest that significant, but transitory, metallicity gradients can develop for systems that have experienced recent (t < 100 Myr) enhanced star formation in their inner discs.

scholarly journals The stellar populations of massive galaxies in the local Universe

2012 ◽  
Vol 8 (S295) ◽  
pp. 290-299
Author(s):  
Richard M. McDermid
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Stellar Population ◽  
Stellar Populations ◽  
Early Type ◽  
Massive Galaxies ◽  
Spatially Resolved ◽  
Low Mass ◽  
Galaxy Environment ◽  
Star Formation Histories

AbstractI present a brief review of the stellar population properties of massive galaxies, focusing on early-type galaxies in particular, with emphasis on recent results from the ATLAS3D Survey. I discuss the occurence of young stellar ages, cold gas, and ongoing star formation in early-type galaxies, the presence of which gives important clues to the evolutionary path of these galaxies. Consideration of empirical star formation histories gives a meaningful picture of galaxy stellar population properties, and allows accurate comparison of mass estimates from populations and dynamics. This has recently provided strong evidence of a non-universal IMF, as supported by other recent evidences. Spatially-resolved studies of stellar populations are also crucial to connect distinct components within galaxies to spatial structures seen in other wavelengths or parameters. Stellar populations in the faint outer envelopes of early-type galaxies are a formidable frontier for observers, but promise to put constraints on the ratio of accreted stellar mass versus that formed ‘in situ’ - a key feature of recent galaxy formation models. Galaxy environment appears to play a key role in controlling the stellar population properties of low mass galaxies. Simulations remind us, however, that current day galaxies are the product of a complex assembly and environment history, which gives rise to the trends we see. This has strong implications for our interpretation of environmental trends.

scholarly journals The cosmic evolution of the stellar mass–velocity dispersion relation of early-type galaxies

2020 ◽  
Vol 498 (1) ◽  
pp. 1101-1120
Author(s):  
Carlo Cannarozzo ◽  
Alessandro Sonnenfeld ◽  
Carlo Nipoti
Keyword(s):  
Mass Velocity ◽  
Selection Criteria ◽  
Velocity Dispersion ◽  
State Of The Art ◽  
Stellar Mass ◽  
Early Type ◽  
Bayesian Hierarchical ◽  
Cosmic Evolution ◽  
Stellar Velocity ◽  
Intrinsic Scatter

ABSTRACT We study the evolution of the observed correlation between central stellar velocity dispersion σe and stellar mass M* of massive ($M_*\gtrsim 3\times 10^{10}\, \mathrm{M_\odot}$) early-type galaxies (ETGs) out to redshift z ≈ 2.5, taking advantage of a Bayesian hierarchical inference formalism. Collecting ETGs from state-of-the-art literature samples, we build a fiducial sample (0 ≲ z ≲ 1), which is obtained with homogeneous selection criteria, but also a less homogeneous extended sample (0 ≲ z ≲ 2.5). Based on the fiducial sample, we find that at z ≲ 1 the M*–σe relation is well represented by $\sigma _{\mathrm{e}}\propto M_*^{\beta }(1+z)^{\zeta}$, with β ≃ 0.18 independent of redshift and ζ ≃ 0.4 (at a given M*, σe decreases for decreasing z, for instance by a factor of ≈1.3 from z = 1 to z = 0). When the slope β is allowed to evolve, we find it increasing with redshift: β(z) ≃ 0.16 + 0.26log (1 + z) describes the data as well as constant β ≃ 0.18. The intrinsic scatter of the M*–σe relation is ≃0.08 dex in σe at given M*, independent of redshift. Our results suggest that, on average, the velocity dispersion of individual massive (M* ≳ 3 × 1011M⊙) ETGs decreases with time while they evolve from z ≈ 1 to z ≈ 0. The analysis of the extended sample, over the wider redshift range 0 ≲ z ≲ 2.5, leads to results similar to that of the fiducial sample, with slightly stronger redshift dependence of the normalization (ζ ≃ 0.5) and weaker redshift dependence of the slope (dβ/dlog (1 + z) ≃ 0.18) when β varies with time. At z = 2 ETGs with $M_*\approx 10^{11}\, \mathrm{M_\odot}$ have, on average, ≈1.7 higher σe than ETGs of similar stellar mass at z = 0.

scholarly journals Insights into formation scenarios of massive early-type galaxies from spatially resolved stellar population analysis in CALIFA

2019 ◽  
Vol 491 (3) ◽  
pp. 3562-3585 ◽  
Author(s):  
Stefano Zibetti ◽  
Anna R Gallazzi ◽  
Michaela Hirschmann ◽  
Guido Consolandi ◽  
Jesús Falcón-Barroso ◽  
...  
Keyword(s):  
Stellar Population ◽  
Population Analysis ◽  
Stellar Mass ◽  
Ex Situ ◽  
Second Phase ◽  
Early Type ◽  
Two Phase ◽  
Spatially Resolved ◽  
Low Metallicity ◽  
Inside Out

ABSTRACT We perform spatially resolved stellar population analysis for a sample of 69 early-type galaxies (ETGs) from the CALIFA integral field spectroscopic survey, including 48 ellipticals and 21 S0’s. We generate and quantitatively characterize profiles of light-weighted mean stellar age and metallicity within ≲2Re, as a function of radius and stellar-mass surface density μ*. We study in detail the dependence of profiles on galaxies’ global properties, including velocity dispersion σe, stellar mass, morphology. ETGs are universally characterized by strong, negative metallicity gradients ($\sim \!-0.3\, \text{dex}$ per Re) within 1Re, which flatten out moving towards larger radii. A quasi-universal local μ*–metallicity relation emerges, which displays a residual systematic dependence on σe, whereby higher σe implies higher metallicity at fixed μ*. Age profiles are typically U-shaped, with minimum around 0.4 Re, asymptotic increase to maximum ages beyond $\sim 1.5\, $Re, and an increase towards the centre. The depth of the minimum and the central increase anticorrelate with σe. A possible qualitative interpretation of these observations is a two-phase scenario. In the first phase, dissipative collapse occurs in the inner 1Re, establishing a negative metallicity gradient. The competition between the outside-in quenching due to feedback-driven winds and some form of inside-out quenching, possibly caused by central AGN feedback or dynamical heating, determines the U-shaped age profiles. In the second phase, the accretion of ex-situ stars from quenched and low-metallicity satellites shapes the flatter stellar population profiles in the outer regions.

scholarly journals Key dynamical results from the SAMI Galaxy Survey

2019 ◽  
Vol 14 (S353) ◽  
pp. 213-221
Author(s):  
Jesse van de Sande ◽  
Joss Bland-Hawthorn ◽  
Dilyar Barat ◽  
Sarah Brough ◽  
Julia J. Bryant ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Stellar Population ◽  
Stellar Mass ◽  
Two Dimensional ◽  
Physical Processes ◽  
Spatially Resolved ◽  
Integral Field Spectroscopy ◽  
Field Spectroscopy ◽  
Gas Measurements ◽  
Integral Field

AbstractWe present an overview of recent key results from the SAMI Galaxy Survey on the build-up of mass and angular momentum in galaxies across morphology and environment. The SAMI Galaxy survey is a multi-object integral field spectroscopic survey and provides a wealth of spatially-resolved, two-dimensional stellar and gas measurements for galaxies of all morphological types, with high-precision due the stable spectral resolution of the AAOmega spectrograph. The sample size of ~3000 galaxies allows for dividing the sample in bins of stellar mass, environment, and star-formation or morphology, whilst maintaining a statistical significant number of galaxies in each bin. By combining imaging, spatially resolved dynamics, and stellar population measurements, our result demonstrate the power of utilising integral field spectroscopy on a large sample of galaxies to further our understanding of physical processes involved in the build-up of stellar mass and angular momentum in galaxies.

scholarly journals The MASSIVE Survey – VII. The relationship of angular momentum, stellar mass and environment of early-type galaxies

2017 ◽  
Vol 471 (2) ◽  
pp. 1428-1445 ◽  
Author(s):  
Melanie Veale ◽  
Chung-Pei Ma ◽  
Jenny E. Greene ◽  
Jens Thomas ◽  
John P. Blakeslee ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Stellar Mass ◽  
Early Type ◽  
Relationship Of ◽  
The Relationship

scholarly journals Stellar masses calibrated with micro-lensed quasars

2014 ◽  
Vol 10 (S311) ◽  
pp. 96-99
Author(s):  
Paul L. Schechter ◽  
Jeffrey A. Blackburne ◽  
David Pooley ◽  
Joachim Wambsganss
Keyword(s):  
Gravitational Potential ◽  
Brown Dwarfs ◽  
Stellar Mass ◽  
Calibration Factor ◽  
Early Type ◽  
Individual Stars ◽  
Red Dwarfs ◽  
Low Mass ◽  
Spectroscopic Signatures ◽  
Stellar Masses

AbstractWe measure the stellar mass surface densities of early type galaxies by observing the micro-lensing of macro-lensed quasars caused by individual stars, including stellar remnants, brown dwarfs and red dwarfs too faint to produce photometric or spectroscopic signatures. Our method measures the graininess of the gravitational potential, in contrast to methods that decompose a smooth total gravitational potential into two smooth components, one stellar and one dark. We find the median likelihood value for the calibration factor $\cal F$ by which Salpeter stellar masses (with a low mass cutoff of 0.1 M⊙) must be multiplied is 1.23, with a one sigma confidence range of 0.77 < $\cal F$ < 2.10.

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