scholarly journals The formation of ultradiffuse galaxies in clusters

2020 ◽  
Vol 494 (2) ◽  
pp. 1848-1858 ◽  
Author(s):  
Laura V Sales ◽  
Julio F Navarro ◽  
Louis Peñafiel ◽  
Eric W Peng ◽  
Sungsoon Lim ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Velocity Dispersion ◽  
Stellar Mass ◽  
Matter Content ◽  
Lower Velocity ◽  
Large Size ◽  
Hydrodynamical Simulation ◽  
Low Surface Brightness ◽  
Mass Size ◽  
Low Surface Brightness Galaxies

ABSTRACT We use the IllustrisTNG cosmological hydrodynamical simulation to study the formation of ultradiffuse galaxies (UDGs) in galaxy clusters. We supplement the simulations with a realistic mass–size relation for galaxies at the time of infall into the cluster, as well as an analytical model to describe the tidally induced evolution of their stellar mass, velocity dispersion, and size. The model assumes ‘cuspy’ NFW haloes and, contrary to recent claims, has no difficulty reproducing the observed number of UDGs in clusters. Our results further suggest that the UDG population consists of a mixture of ‘normal’ low surface brightness galaxies such as those found in the field (‘born’ UDGs, or B-UDGs), as well as a distinct population that owe their large size and low surface brightness to the effects of cluster tides (‘tidal’, or T-UDGs). The simulations indicate that T-UDGs entered the cluster earlier and should be more prevalent than B-UDGs near the cluster centres. T-UDGs should also have, at given stellar mass, lower velocity dispersion, higher metallicities, and lower dark matter content than B-UDGs. Our results suggest that systems like DF-44 are consistent with having been born as UDGs, while others such as DF2, DF4, and VLSB-D are possibly extreme T-UDG examples.

scholarly journals The σc — Vcirc correlation in high and low surface brightness galaxies

2004 ◽  
Vol 220 ◽  
pp. 339-340 ◽  
Author(s):  
A. Pizzella ◽  
E. Dalla Bontà ◽  
E. M. Corsini ◽  
L. Coccato ◽  
F. Bertola
Keyword(s):  
Surface Brightness ◽  
Velocity Dispersion ◽  
Spiral Galaxies ◽  
High Surface ◽  
Linear Scale ◽  
High Surface Brightness ◽  
Circular Velocity ◽  
Straight Line ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies

We investigate the relation between the central velocity dispersion, σc, and the circular velocity, Vcirc, in galaxies. in addition to previously obtained data, we consider an observationally homogeneus sample of 52 high surface brightness and 11 low surface brightness spiral galaxies. We performed a straight line regression analysis in a linear scale, finding a good fit, also for low σc galaxies, always rejected in the previous studies. Low surface brightness galaxies seem to behave differently, showing either higher values of Vcirc or lower values of σc with respect to their high surface brightness counterparts.

scholarly journals Investigating the AGN activity and black hole masses in low surface brightness galaxies

2014 ◽  
Vol 10 (S312) ◽  
pp. 31-35
Author(s):  
Smitha Subramanian ◽  
Ramya Sethuram ◽  
Mousumi Das ◽  
Koshy George ◽  
Sivarani Thirupathi ◽  
...  
Keyword(s):  
Black Hole ◽  
Surface Brightness ◽  
Velocity Dispersion ◽  
Sloan Digital Sky Survey ◽  
Stellar Spectra ◽  
Low Surface Brightness ◽  
Stellar Velocity ◽  
Low Mass ◽  
Using Data ◽  
Low Surface Brightness Galaxies

AbstractWe present an analysis of the optical nuclear spectra from the active galactic nuclei (AGN) in a sample of giant low surface brightness (GLSB) galaxies. GLSB galaxies are extreme late type spirals that are large, isolated and poorly evolved compared to regular spiral galaxies. Earlier studies have indicated that their nuclei have relatively low mass black holes. Using data from the Sloan Digital Sky Survey (SDSS), we selected a sample of 30 GLSB galaxies that showed broad Hα emission lines in their AGN spectra. In some galaxies such as UGC 6284, the broad component of Hα is more related to outflows rather than the black hole. One galaxy (UGC 6614) showed two broad components in Hα, one associated with the black hole and the other associated with an outflow event. We derived the nuclear black hole (BH) masses of 29 galaxies from their broad Hα parameters. We find that the nuclear BH masses lie in the range 105 – 107 M⊙. The bulge stellar velocity dispersion σe was determined from the underlying stellar spectra. We compared our results with the existing BH mass - velocity dispersion (MBH–σe) correlations and found that the majority of our sample lie in the low BH mass regime and below the MBH–σe correlation. The effects of galaxy orientation in the measurement of σe and the increase of σe due to the effects of bar are probable reasons for the observed offset for some galaxies, but in many galaxies the offset is real. A possible explanation for the MBH–σe offset could be lack of mergers and accretion events in the history of these galaxies which leads to a lack of BH-bulge co-evolution.

scholarly journals The origin of low-surface-brightness galaxies in the dwarf regime

2021 ◽  
Vol 502 (3) ◽  
pp. 4262-4276
Author(s):  
R A Jackson ◽  
G Martin ◽  
S Kaviraj ◽  
M Ramsøy ◽  
J E G Devriendt ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
High Surface ◽  
Stellar Mass ◽  
Current Data ◽  
Sloan Digital Sky Survey ◽  
Data Sets ◽  
Low Surface Brightness ◽  
Gas Accretion ◽  
Low Surface Brightness Galaxies

ABSTRACT Low-surface-brightness galaxies (LSBGs) – defined as systems that are fainter than the surface-brightness limits of past wide-area surveys – form the overwhelming majority of galaxies in the dwarf regime (M⋆ < 109 M⊙). Using NewHorizon, a high-resolution cosmological simulation, we study the origin of LSBGs and explain why LSBGs at similar stellar mass show the large observed spread in surface brightness. NewHorizon galaxies populate a well-defined locus in the surface brightness–stellar mass plane, with a spread of ∼3 mag arcsec−2, in agreement with deep Sloan Digital Sky Survey (SDSS) Stripe 82 data. Galaxies with fainter surface brightnesses today are born in regions of higher dark matter density. This results in faster gas accretion and more intense star formation at early epochs. The stronger resultant supernova feedback flattens gas profiles at a faster rate, which, in turn, creates shallower stellar profiles (i.e. more diffuse systems) more rapidly. As star formation declines towards late epochs ( z < 1), the larger tidal perturbations and ram pressure experienced by these systems (due to their denser local environments) accelerate the divergence in surface brightness, by increasing their effective radii and reducing star formation, respectively. A small minority of dwarfs depart from the main locus towards high surface brightnesses, making them detectable in past wide surveys (e.g. standard-depth SDSS images). These systems have anomalously high star formation rates, triggered by recent fly-by or merger-driven starbursts. We note that objects considered extreme or anomalous at the depth of current data sets, e.g. ‘ultra-diffuse galaxies’, actually dominate the predicted dwarf population and will be routinely visible in future surveys like the Legacy Survey of Space and Time (LSST).

scholarly journals Probes of Low Surface Brightness Galaxies through Low Frequency Spectroscopy with GMRT

2002 ◽  
Vol 199 ◽  
pp. 110-113
Author(s):  
D. Narasimha ◽  
S.M. Chitre
Keyword(s):  
Surface Brightness ◽  
Low Frequency ◽  
Rotation Velocity ◽  
Gravitational Lens ◽  
Complete Sample ◽  
Low Surface Brightness ◽  
Mass Size ◽  
Analysis Of The Images ◽  
Low Surface Brightness Galaxies ◽  
The Universe

Low Surface Brightness galaxies (LSBs) may well constitute an important component of the Universe and a good fraction of baryons may even be locked up in their gravitational potential. Existence of such massive objects was predicted from an investigation of gravitational lens systems more than a decade ago (Narasimha & Chitre, 1989). There are more compelling reasons for believing their universality based on the of the analysis of the images around the cusp caustics in some of the well-studied lenses. A complete sample of the mass, size and rotation velocity of LSBs in our neighbourhood, as well as in a limited volume at a larger redshift will be important for estimation of power spectrum as well as evolution of structures in the Universe. The GMRT type instrument is ideally suited for detection and study of the LSBs. We expect to detect 21 cm emission from around 2 to 10 LSBs per beam of GMRT dish at the level of 5 mJy flux with a survey covering 30 Mhz bandwidth, if their line width is of the order of 30 km/sec.

scholarly journals The first detection of ultra-diffuse galaxies in the Hydra I cluster from the VEGAS survey

2020 ◽  
Vol 642 ◽  
pp. A48
Author(s):  
E. Iodice ◽  
M. Cantiello ◽  
M. Hilker ◽  
M. Rejkuba ◽  
M. Arnaboldi ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Total Population ◽  
Matter Content ◽  
Early Type ◽  
Low Surface Brightness ◽  
Colour Distribution ◽  
Specific Frequency ◽  
Stellar Masses ◽  
Low Surface Brightness Galaxies ◽  
Early Type Galaxy

In this paper, we report the discovery of 27 low-surface brightness galaxies, of which 12 are candidates for ultra-diffuse galaxies (UDG) in the Hydra I cluster, based on deep observations taken as part of the VST Early-type Galaxy Survey (VEGAS). This first sample of UDG candidates in the Hydra I cluster represents an important step in our project that aims to enlarge the number of confirmed UDGs and, through study of statistically relevant samples, constrain the nature and formation of UDGs. This study presents the main properties of this class of galaxies in the Hydra I cluster. For all UDGs, we analysed the light and colour distribution, and we provide a census of the globular cluster (GC) systems around them. Given the limitations of a reliable GC selection based on two relatively close optical bands only, we find that half of the UDG candidates have a total GC population consistent with zero. Of the other half, two galaxies have a total population larger than zero at 2σ level. We estimate the stellar mass, the total number of GCs, and the GC specific frequency (SN). Most of the candidates span a range of stellar masses of 107 − 108 M⊙. Based on the GC population of these newly discovered UDGs, we conclude that most of these galaxies have a standard or low dark matter content, with a halo mass of ≤1010 M⊙.

scholarly journals How “cold” are the stellar discs of superthin galaxies?

2021 ◽  
Author(s):  
K Aditya ◽  
Arunima Banerjee
Keyword(s):  
Vertical Velocity ◽  
Surface Brightness ◽  
Velocity Dispersion ◽  
Dark Matter Halo ◽  
Galactic Disc ◽  
Stellar Disc ◽  
Disc Model ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies ◽  
Scale Length

Abstract Superthin galaxies are a class of bulgeless, low surface brightness galaxies with strikingly high values of planar-to-vertical axes ratio $\rm (b/a> 10 - 20)$, possibly indicating the presence of an ultra-cold stellar disc. Using the multi-component galactic disc model of gravitationally-coupled stars and gas in the force field of the dark matter halo as well as the stellar dynamical code AGAMA (Action-based Galaxy Modelling Architecture), we determine the vertical velocity dispersion of stars and gas as a function of galacto-centric radius for five superthin galaxies (UGC 7321, IC 5249, FGC 1540, IC2233 and UGC00711) using observed stellar and atomic hydrogen (HI) scale heights as constraints, using a Markov Chain Monte Carlo Method. We find that the central vertical velocity dispersion for the stellar disc in the optical band varies between σ0s ∼ 10.2 − 18.4 $\rm {kms}^{-1}$ and falls off with an exponential scale length of 2.6 to 3.2 Rd where Rd is the exponential stellar disc scale length. Interestingly, in the 3.6 μm, the same, averaged over the two components of the stellar disc, varies between 5.9 to 11.8 $\rm {kms}^{-1}$, both of which confirm the presence of ”ultra-cold” stellar discs in superthin galaxies. Interestingly, the global median of the multi-component disc dynamical stability parameter QN of our sample superthins is found to be 5 ± 1.5, which higher than the global median value of 2.2 ± 0.6 for a sample

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