The Rastall gravity is a modification of Einstein's general relativity, in which the energy-momentum conservation is not satisfied and depends on the gradient of the Ricci curvature. It is in dispute whether the Rastall gravity is equivalent to the general relativity (GR). In this work, we constrain the theory using the rotation curves of Low Surface Brightness (LSB) spiral galaxies. Through fitting the rotation curves of LSB galaxies, we obtain the parameter $β$ of the Rastall gravity. The $β$ values of LSB galaxies satisfy Weak Energy Condition (WEC) and Strong Energy Condition(SEC). Combining the $β$ values of type Ia supernovae and gravitational lensing of elliptical galaxies on the Rastall gravity, we conclude that the Rastall gravity is equivalent to the general relativity.
Recently, Rastall gravity is undergoing a significant surge in popularity. We obtain a power-law total mass-density profile for the inner region (within several effective radius) of early-type galaxies (ETGs) from the space-time structures which are described by the static spherically-symmetric solutions of Rastall gravity under the assumption of perfect fluid matter. We find that in the inner region of ETGs, the Rastall dimensionless parameter $β=κλ$ determines the mass distribution. We then use 118 galaxy-galaxy strong gravitational lensing systems to constrain the Rastall dimensionless para…
Giant low surface brightness galaxies (gLSBGs) with the disk radii of up to 130 kpc represent a challenge for currently accepted theories of galaxy formation and evolution, because it is difficult to build-up such large dynamically cold systems via mergers preserving extended disks. We summarize the in-depth study of the sample of 7 gLSBGs based on the results of the performed spectral long-slit observations at the Russian 6-m BTA telescope of SAO RAS, surface photometry and HI data available in literature. Our study revealed that most gLSBGs do not deviate from the Tully-Fisher relation. We d…
Probing sub-galactic mass structure with the power spectrum of surface-brightness anomalies in high-resolution observations of galaxy-galaxy strong gravitational lenses. II.Observational constraints on the sub-galactic matter power spectrum
Probing sub-galactic mass structure with the power spectrum of surface-brightness anomalies in high-resolution observations of galaxy-galaxy strong gravitational lenses. I. Power-spectrum measurement and feasibility study
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 ga…
Star-forming dwarfs are studied to elucidate the physical underpinnings of their fundamental plane. It is confirmed that residuals in the Tully-Fisher relation are correlated with surface brightness, but that even after accommodating the surface brightness dependence through the dwarf fundamental plane, residuals in absolute magnitude are far larger than expected from observational errors. Rather, a more fundamental plane is identified which connects the potential to HI line width and surface brightness. Residuals correlate with the axis ratio in a way which can be accommodated by recognizing …
Surface Brightness Fluctuations (SBF) can provide useful information about the unresolved stellar content of early-type galaxies and spiral bulges. The absolute SBF magnitude Mbar in a given passband depends on the properties of the stellar population and can be predicted by population synthesis models. SBF measurements in different bandpasses are sensitive to different evolutionary stages within the galaxy stellar population. Near-IR SBF magnitudes are sensitive to the evolution of stars within the AGB phase, especially the thermally pulsing AGB, while SBF in the blue and UV are sensitive to …
Understanding the formation and evolution of low surface brightness galaxies (LSBGs) is critical for explaining their wide-ranging properties. However, studies of LSBGs in deep photometric surveys are often hindered by a lack of distance estimates. In this work, we present a new catalogue of 479 LSBGs, identified in deep optical imaging data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). These galaxies are found across a range of environments, from the field to groups. Many are likely to be ultra-diffuse galaxies (UDGs). We see clear evidence for a bimodal population in colour …
The low surface brightness galaxies are gas-rich and yet have a low star formation rate, this is a well-known puzzle. The spiral features in these galaxies are weak and difficult to trace, although this aspect has not been studied much. These galaxies are known to be dominated by the dark matter halo from the innermost regions. Here we do a stability analysis for the galactic disc of UGC 7321, a low surface brightness, superthin galaxy, for which the various observational input parameters are available. We show that the disc is stable against local, linear axisymmetric and non-axisymmetric per…
In the context of modified Newtonian dynamics, the fundamental plane, as the observational signature of the Newtonian virial theorem, is defined by high surface brightness objects that deviate from being purely isothermal: the line-of-sight velocity dispersion should slowly decline with radius as observed in luminous elliptical galaxies. All high surface brightness objects (e.g. globular clusters, ultra-compact dwarfs) will lie, more or less, on the fundamental plane defined by elliptical galaxies, but low surface brightness objects (dwarf spheroidals) would be expected to deviate from this re…
To gain insights into long-term Active Galactic Nuclei (AGN) variability, we analyze an AGN sample from the Sloan Digital Sky Survey (SDSS) and compare their photometry with observations from the Hyper Suprime-Cam survey (HSC) observed $\langle 14.85 \rangle$ years after SDSS. On average, the AGN are fainter in HSC than SDSS. We demonstrate that the difference is not due to subtle differences in the SDSS versus HSC filters or photometry. The decrease in mean brightness is redshift dependent, consistent with expectations for a change that is a function of the rest-frame time separation between …
X-ray selected samples are known to miss galaxy clusters that are gas poor and have a low surface brightness. This is different for the optically selected samples such as the X-ray Unbiased Selected Sample (XUCS). We characterise the origin of galaxy clusters that are gas poor and have a low surface-brightness by studying covariances between various cluster properties at fixed mass using hydrodynamic cosmological simulations. We extracted approx. 1800 galaxy clusters from a high-resolution Magneticum hydrodynamic cosmological simulation and computed covariances at fixed mass of the following p…
We outline a general procedure for simulating the surface brightness of astrophysical jets (and other astronomical objects) by post-processing gas dynamical simulations of densities and temperatures using spectral line emission data from the astrophysical spectral synthesis package {\em Cloudy}. Then we validate the procedure by comparing the simulated surface brightness of the HH~30 astrophysical jet in the forbidden [O~I], [N~II], and [S~II] doublets with {\em Hubble Space Telescope}\/ observations of Hartigan and Morse and multiple-ion magnetohydrodynamic simulations of Tesileanu et al. The…
Context. The assembly history of the stellar component of a massive elliptical galaxy is closely related to that of its dark matter halo. Measuring how the properties of galaxies correlate with their halo mass can help understand their evolution. Aims. We investigate how the dark matter halo mass of elliptical galaxies varies as a function of their properties, using weak gravitational lensing observations. To minimise the chances of biases, we focus on galaxy properties that can be determined robustly: the surface brightness profile and the colour. Methods. We selected 2409 central massive ell…
The absence of stellar disc truncations in low-inclined spiral galaxies has been a matter of debate in the last decade. Disc truncations are often observed in highly inclined galaxies but no obvious detection of this feature has so far been made in face-on spirals. Here we show, using a simple exponential disc plus stellar halo model based on current observational constraints, that truncations in face-on projections occur at surface brightness levels comparable to the brightness of stellar haloes at the same radial distance. In this sense, stellar haloes outshine the galaxy disc at the expecte…
In this paper, we report the new results of spectroscopic observations of $γ$-ray blazar S5 0716+714 from 2019 September to 2020 March with the 2.4 m optical telescope at Lijiang Observatory of Yunnan Observatories. The median cadence of observations is $\sim$ 1 day. During the second observation period (Epoch2), the observational data reveal an extremely bright state and a bluer-when-brighter (BWB) chromatism. The BWB trend of Epoch2 differs significantly from that of the first observation period (Epoch1). A significantly brightness-dependent BWB chromatism emerges in the total data of Epoch1…
Direct N-body calculations are presented of the early evolution of exposed clusters to quantify the influence of gas expulsion on the time-varying surface brightness. By assuming that the embedded OB stars drive out most of the gas after a given time delay, the change of the surface brightness of expanding star clusters is studied. The influence of stellar dynamics and stellar evolution is discussed. The growth of the core radii of such models shows a remarkable core re-virialisation. The decrease of the surface mass density during gas expulsion is large and is only truncated by this re-virial…
We use the low surface brightness galaxy (LSBG) samples created from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP, 781 galaxies), the Dark Energy Survey (DES, 20977 galaxies), and the Legacy Survey (selected via HI detection in the Arecibo Legacy Fast ALFA Survey, 188 galaxies) to infer the intrinsic shape distribution of the low surface brightness galaxy population. To take into account the effect of the surface brightness cuts employed when constructing LSBG samples, we simultaneously model both the projected ellipticity and the apparent surface brightness in our shape inference. …
Dark matter (DM) is one of the biggest mystery in the Universe. In this review, after a brief discussion of the DM evidences and the main proposed candidates and scenarios for the DM phenomenon, we focus on recent results on rotating disc galaxies giving a special attention to the Low Surface Brightness (LSB) galaxies. The main observational properties related to the baryonic matter in LSBs, investigated over the last decades, are briefly recalled. Next, the LSBs are analysed by means of the mass modelling of their rotation curves both individually and stacked. The latter analysis, via the Uni…
The connection between the bulge mass or bulge luminosity in disk galaxies and the number, spatial and phase space distribution of associated dwarf galaxies is a discriminator between cosmological simulations related to galaxy formation in cold dark matter and generalized gravity models. Here, a nearby sample of isolated Milky Way class edge-on galaxies is introduced, to facilitate observational campaigns to detect the associated families of dwarf galaxies at low surface brightness. Three galaxy pairs with at least one of the targets being edge-on are also introduced. About 60% of the catalogu…
The formation scenario for giant low surface brightness (gLSB) galaxies with discs as large as 100 kpc still remains unclear. These stellar systems are rare and very hard to observe, therefore a detailed insight on every additional object helps to understand their nature. Here we present a detailed observational study of the gLSB UGC 1922 performed using deep optical imaging and spectroscopic observations combined with archival ultraviolet data. We derived spatially resolved properties of stellar and ionized gas kinematics and characteristics of stellar populations and interstellar medium. We …
A large fraction of the baryonic matter in the Universe is located in filaments in the intergalactic medium. However, the low surface brightness of these filaments has not yet allowed their direct detection except in very special regions in the circum-galactic medium (CGM). Here we simulate the intensity and spatial fluctuations in Lyman Alpha ${\rm (Lyα)}$ emission from filaments in the intergalactic medium (IGM) and discuss the prospects for the next generation of space based instruments to detect the low surface brightness universe at UV wavelengths. Starting with a high resolution N-body s…
We analyse the surface brightness profiles of disc-type galaxies in the EAGLE simulations in order to investigate the effects of galaxy mass and environment on galaxy profile types. Following observational works, we classify the simulated galaxies by their disc surface brightness profiles into single exponential (Type I), truncated (Type II) and anti-truncated (Type III) profiles. In agreement with previous observation and theoretical work, we find that Type II discs result from truncated star-forming discs that drive radial gradients in the stellar populations. In contrast, Type III profiles …
We examine the role of the interstellar magnetic field to modulate the orientation of turbulent flows within the Taurus molecular cloud using spatial gradients of thin velocity slices of 12CO and 13CO antenna temperatures. Our analysis accounts for the random errors of the gradients that arise from the thermal noise of the spectra. The orientations of the vectors normal to the antenna temperature gradient vectors are compared to the magnetic field orientations that are calculated from Planck 353~GHz polarization data. These relative orientations are parameterized with the projected Rayleigh st…
We build a volume-limited sample of galaxies derived from the SDSS-DR7 to characterize several physical properties of the dark matter halos where LSB galaxies reside. Using an observational proxy for the assembly time, we found that LSB galaxies assembly half of their total halo mass later than HSB ones, reinforcing the idea of them being unevolved systems. We use 5 different methods to estimate the total halo mass, finding that the total stellar-to-halo mass ratio is up to 22% lower in LSB galaxies. Finally, in order to estimate the spin parameter, we use a bulge+disk decomposition to obtain …
Searching for low-surface-brightness galaxies with compact neural networks A parameter-efficient approach to first-pass selection of diffuse galaxy in HSC-SSP imaging
