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

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 Massive low-surface-brightness galaxies in the eagle simulation

2020 ◽  
Vol 496 (3) ◽  
pp. 3996-4016
Author(s):  
Andrea Kulier ◽  
Gaspar Galaz ◽  
Nelson D Padilla ◽  
James W Trayford
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Surface Density ◽  
Surface Brightness ◽  
Initial Conditions ◽  
High Surface ◽  
Formation Rate ◽  
Dark Matter Halo ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies

ABSTRACT We investigate the formation and properties of low surface brightness galaxies (LSBGs) with M* > 109.5 M⊙ in the eagle hydrodynamical cosmological simulation. Galaxy surface brightness depends on a combination of stellar mass surface density and mass-to-light ratio (M/L), such that low surface brightness is strongly correlated with both galaxy angular momentum (low surface density) and low specific star formation rate (high M/L). This drives most of the other observed correlations between surface brightness and galaxy properties, such as the fact that most LSBGs have low metallicity. We find that LSBGs are more isolated than high-surface-brightness galaxies (HSBGs), in agreement with observations, but that this trend is driven entirely by the fact that LSBGs are unlikely to be close-in satellites. The majority of LSBGs are consistent with a formation scenario in which the galaxies with the highest angular momentum are those that formed most of their stars recently from a gas reservoir co-rotating with a high-spin dark matter halo. However, the most extended LSBG discs in EAGLE, which are comparable in size to observed giant LSBGs, are built up via mergers. These galaxies are found to inhabit dark matter haloes with a higher spin in their inner regions (<0.1r200c), even when excluding the effects of baryonic physics by considering matching haloes from a dark-matter-only simulation with identical initial conditions.

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 Observational insights on the origin of giant low surface brightness galaxies

2021 ◽  
Vol 503 (1) ◽  
pp. 830-849
Author(s):  
Anna S Saburova ◽  
Igor V Chilingarian ◽  
Anastasia V Kasparova ◽  
Olga K Sil’chenko ◽  
Kirill A Grishin ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Surface Brightness ◽  
High Surface ◽  
Dark Matter Halo ◽  
High Mass ◽  
Formation Mechanisms ◽  
Orbital Parameters ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies

ABSTRACT Giant low surface brightness galaxies (gLSBGs) with dynamically cold stellar discs reaching the radius of 130 kpc challenge currently considered galaxy formation mechanisms. We analyse new deep long-slit optical spectroscopic observations, archival optical images, and published Hi and optical spectroscopic data for a sample of seven gLSBGs, for which we performed mass modelling and estimated the parameters of dark matter haloes assuming the Burkert dark matter density profile. Our sample is not homogeneous by morphology, parameters of stellar populations, and total mass, however, six of seven galaxies sit on the high-mass extension of the baryonic Tully–Fisher relation. In UGC 1382, we detected a global counterrotation of the stellar high surface brightness (HSB) disc with respect to the extended LSB disc. In UGC 1922 with signatures of a possible merger, the gas counterrotation is seen in the inner disc. Six galaxies host active galactic nuclei, three of which have the estimated black hole masses substantially below those expected for their (pseudo-)bulge properties suggesting poor merger histories. Overall, the morphology, internal dynamics, and low star formation efficiency in the outer discs indicate that the three formation scenarios shape gLSBGs: (i) a two-stage formation when an HSB galaxy is formed first and then grows an LSB disc by accreting gas from an external supply; (ii) an unusual shallow and extended dark matter halo; (iii) a major merger with fine-tuned orbital parameters and morphologies of the merging galaxies.

scholarly journals The prediction of rotation curves in gas-dominated dwarf galaxies with modified dynamics

2019 ◽  
Vol 485 (1) ◽  
pp. 513-521 ◽  
Author(s):  
R H Sanders
Keyword(s):  
Surface Density ◽  
Surface Brightness ◽  
Dark Halo ◽  
Baryonic Matter ◽  
Rotation Curves ◽  
Stellar Disc ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies

ABSTRACT I consider the observed rotation curves of 12 gas-dominated low-surface-brightness galaxies – objects in which the mass of gas ranges between 2.2 and 27 times the mass of the stellar disc (mean = 9.4). This means that, in the usual decomposition of rotation curves into those resulting from various mass components, the mass-to-light ratio of the luminous stellar disc effectively vanishes as an additional adjustable parameter. It is seen that the observed rotation curves reflect the observed structure in gas surface density distribution often in detail. This fact is difficult to comprehend in the context of the dark matter paradigm where the dark halo completely dominates the gravitational potential in the low surface density systems; however it is an expected result in the context of modified Newtonian dynamics (MOND) in which the baryonic matter is the only component. With MOND the calculated rotation curves are effectively parameter-free predictions.

A full pipeline for modelling low surface brightness galaxies

2019 ◽  
Vol 14 (S353) ◽  
pp. 279-280
Author(s):  
Marius Peper ◽  
Boudewijn F. Roukema ◽  
Krzysztof Bolejko
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Surface Brightness ◽  
Dark Matter Halo ◽  
Cosmological Simulations ◽  
Galaxy Formation And Evolution ◽  
Low Surface Brightness ◽  
Formation And Evolution ◽  
Low Surface Brightness Galaxies

AbstractCosmological simulations are a powerful tool to test various cosmological and galaxy formation scenarios. The discovery of low surface brightness objects has been a challenge for both of these fields. Our work aims to create a fully reproducible pipeline to generate a realistic dark matter halo catalog with corresponding information on galaxy formation and evolution.

scholarly journals The universal rotation curve of low surface brightness galaxies – IV. The interrelation between dark and luminous matter

2019 ◽  
Vol 490 (4) ◽  
pp. 5451-5477 ◽  
Author(s):  
Chiara Di Paolo ◽  
Paolo Salucci ◽  
Adnan Erkurt
Keyword(s):  
Dark Matter ◽  
Surface Brightness ◽  
Rotation Curve ◽  
High Surface ◽  
Dark Matter Halo ◽  
Rotation Curves ◽  
Central Surface ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies ◽  
Lsb Galaxies

ABSTRACT We investigate the properties of the baryonic and the dark matter components in low surface brightness (LSB) disc galaxies, with central surface brightness in the B band $\mu _0 \ge 23 \, \mathrm{mag \, arcsec}^{-2}$. The sample is composed of 72 objects, whose rotation curves show an orderly trend reflecting the idea of a universal rotation curve (URC) similar to that found in the local high surface brightness (HSB) spirals in previous works. This curve relies on the mass modelling of the co-added rotation curves, involving the contribution from an exponential stellar disc and a Burkert cored dark matter halo. We find that the dark matter is dominant especially within the smallest and less luminous LSB galaxies. Dark matter haloes have a central surface density $\Sigma _0 \sim 100 \, \mathrm{M}_{\odot } \, \mathrm{pc}^{-2}$, similar to galaxies of different Hubble types and luminosities. We find various scaling relations among the LSBs structural properties which turn out to be similar but not identical to what has been found in HSB spirals. In addition, the investigation of these objects calls for the introduction of a new luminous parameter, the stellar compactness C* (analogously to a recent work by Karukes & Salucci), alongside the optical radius and the optical velocity in order to reproduce the URC. Furthermore, a mysterious entanglement between the properties of the luminous and the dark matter emerges.

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.

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