Search

The Virgo Cluster is the nearest substantial cluster of galaxies to the Milky Way and a cornerstone of the extragalactic distance scale. Here, we present JWST/NIRCam observations that simultaneously cover the cores and halos of ten galaxies in and around the Virgo Cluster and are designed to perform simultaneous measurements of the tip of the red giant branch (TRGB) and surface brightness fluctuations (SBF). Seven of the targets are within the Virgo Cluster and where we are able to resolve some of the cluster's substructure, while an additional three provide important constraints on Virgo infall. The seven galaxies within Virgo itself all have SBF measurements from the Advanced Camera for Surveys Virgo Cluster Survey (ACSVCS). After adjusting the ACSVCS measurements for the offset from our new JWST TRGB measurements, we determine a distance to the Virgo Cluster of d $=$ 16.17 $\pm$ 0.25 (stat) $\pm$ 0.47 (sys) Mpc. The work presented here is part of a larger program to develop a Population II distance scale through the TRGB and SBF that is completely independent of the prominent Cepheid + Type Ia supernova ladder. The TRGB distances to the galaxies presented here, when combined with future SBF measurements, will provide a crucial step forward for determining whether or not systematic errors can explain the well-known "Hubble tension'' or if there is significant evidence for cracks in the $\Lambda$CDM model., Comment: submitted to ApJ. comments welcome and appreciated. program name has changed from Paper I's "The Population II Extragalactic Distance Scale" to "The TRGB-SBF Project"

Stellar tidal streams are a key tracer of galaxy evolution and have the potential to provide an indirect means for tracing dark matter. For the Local Group, many diffuse substructures have been identified and their link to galaxy evolution has been traced. However, an analysis of a larger sample is required to better probe the frequency and characteristics of these streams to verify the predictions of the Lambda-CDM model and its implementation in cosmological simulations. For that purpose, we are carrying out the first systematic survey of faint stellar debris from tidally disrupted dwarf satellites around nearby galaxies up to a distance of 100 Mpc. In this paper, we present a catalogue with the results of the first harvest of stellar tidal streams found by visual inspection in deep images of ~ 700 galaxies from the Dark Energy Survey (DES). We include a photometric characterisation of the streams obtained by measuring their surface brightnesses and colours. We found a total of 63 streams in our sample at distances between 40 and 100 Mpc, including 59 which were not previously reported. We measured their average surface brightness for the grz bands, to be 28.35+/-0.20, 27.81+/-0.13 and 27.62+/-0.09 mag arcsec^-2, respectively. By applying a statistical analysis to our findings, we obtained a stream detection frequency of 9.1% +/- 1.1% , in agreement with previous studies. We identified stream progenitors in 5-14% of our stream sample, depending on the confidence level. The first catalogue of streams in the Local Universe presented here will be complemented by future stream surveys within the Stellar Stream Legacy Survey. In this work we have learnt that the faintest measured stream surface brightness can be significantly brighter than the surface brightness limit of an image measured at pixel level, mainly due to correlated noise present in the images., Comment: 20 pages with 16 figures, plus Appendices: 27 pages in total

The problem of missing satellites still remains one of the well-known problems of the Lambda-CDM cosmological theory. Despite significant progress in cosmological modeling achieved in recent years, the search for new dwarf galaxies-satellites of nearby giant galaxies remains extremely important. In this series of papers we report the first results of an on-going systematic survey of faint dwarf spheroidal galaxies in the vicinity of the bright late-type spiral NGC 253 galaxy, the brightest member of the Sculptor filament located at a distance of 3.7 Mpc. We performed a new NGC 253 satellite search by means of visual inspection using co-added image cutouts reprocessed in the DESI Legacy image surveys, reaching a very low surface brightness regime (28.0--29.0 mag arcsec-2). Five new dwarf galaxies have been discovered in the vicinity of NGC 253, that we named them Do V, Do VI, Do VII, Do VIII and Do IX. Assuming they are associated to NGC 253, their total absolute V-magnitudes fall in the -7 to -9 mag range, which is typical for dwarf satellites in the local Universe. The central surface brightness tend to be extremely low for all the discovered dwarfs and fall roughly in the range of 25--26 mag arcsec-2 in g-band. We present a new list of galaxies located around the giant spiral NGC 253. With the inclusion of these additional satellites, the overall spatial distribution of the system becomes less flattened and is now broadly consistent with analogs drawn from Lambda-CDM expectations. Interestingly, the distribution appears to be rather lopsided. Yet, firm conclusions on the presence of absence of a correlated satellite structure are hampered since distance information is lacking, the census of observed dwarfs in the system remains far from complete, and spectroscopic velocities are not even available for most known satellites., Comment: 10 pages, 6 figures, 4 Tables, submitted to Astronomy and Astrophysics

Differences between the local value of the Hubble constant measured via the distance ladder versus the value inferred from the cosmic microwave background with the assumption of the standard $\Lambda$CDM model have reached over 5$\sigma$ significance. To determine if this discrepancy is due to new physics or more mundane systematic errors, it is essential to remove as many sources of systematic uncertainty as possible by developing high-precision distance ladders that are independent of the traditional Cepheid and Type Ia supernovae route. Here we present JWST observations of three early-type Fornax Cluster galaxies, the first of fourteen observations from a Cycle 2 JWST program. Our modest integration times allow us to measure highly precise tip of the red giant branch (TRGB) distances, and will also be used to perform measurements of Surface Brightness Fluctuations (SBF). From these three galaxies, we determine an average TRGB distance modulus to the Fornax Cluster of $\mu$ = 31.424 $\pm$ 0.077 mag, or D = 19.3 $\pm$ 0.7 Mpc. With eleven more scheduled observations in nearby elliptical galaxies, our program will allow us set the zero point of the SBF scale to better than 2$\%$ for more distant measurements, charting a path towards a high-precision measurement of $H_{0}$ that is independent of the traditional Cepheid-SN Ia distance ladder., Comment: 14 pages, 9 figures, accepted to ApJ

We present a new method - called HINORA (HIgh-NOise RANdom SAmple Consensus) - for the identification of regular structures in 3D point distributions. Motivated by the possible existence of the so called Council of Giants, i.e. a ring of twelve massive galaxies surrounding the Local Group in the Local Sheet with a radius of 3.75 Mpc, we apply HINORA to the Local Volume Galaxy catalogue confirming its existence. When varying the lower limit of K-band luminosity of the galaxy entering the catalogue, we further report on the existence of another ring-like structure in the Local Volume that now contains the Milky Way and M31. However, this newly found structure is dominated by low-mass (satellite) galaxies. While we here simply present the novel method as well as its first application to observational data, follow-up work using numerical simulations of cosmic structure formation shall shed light into the origin of such regular patterns in the galaxy distribution. Further, the method is equally suited to identify similar (or even different) structures in various kinds of astrophysical data (e.g. locating the actual 'baryonic-acoustic oscillation spheres' in galaxy redshift surveys)., Comment: Accepted for publication in PASA

The tip of the red giant branch (TRGB) allows for the measurement of precise and accurate distances to nearby galaxies, based on the brightest ascent of low-mass red giant branch stars before they undergo the helium flash. With the advent of JWST, there is great promise to utilize the technique to measure galaxy distances out to at least 50 Mpc, significantly further than HST's reach of 20 Mpc. However, with any standard candle, it is first necessary to provide an absolute reference. Here we use Cycle 1 data to provide an absolute calibration in the F090W filter. F090W is most similar to the F814W filter commonly used for TRGB measurements with HST, which had been adopted by the community due to minimal dependence from the underlying metallicities and ages of stars. The imaging we use was taken in the outskirts of NGC 4258, which has a direct geometrical distance measurement from the Keplerian motion of its water megamaser. Utilizing several measurement techniques, we find $M_{TRGB}^{F090W}$ = -4.362 $\pm$ 0.033 (stat) $\pm$ 0.045 (sys) mag (Vega) for the metal-poor TRGB. We also perform measurements of the TRGB in two Type Ia supernova hosts, NGC 1559, and NGC 5584. We find good agreement between our TRGB distances and previous distance determinations to these galaxies from Cepheids ($\Delta$ = 0.01 $\pm$ 0.06 mag), with these differences being too small to explain the Hubble tension ($\sim$0.17 mag). As a final bonus, we showcase the serendipitous discovery of a faint dwarf galaxy near NGC 5584., Comment: 20 pages, 12 figures, accepted to ApJ

When a gait of a bipedal robot is developed using deep reinforcement learning, reference trajectories may or may not be used. Each approach has its advantages and disadvantages, and the choice of method is up to the control developer. This paper investigates the effect of reference trajectories on locomotion learning and the resulting gaits. We implemented three gaits of a full-order anthropomorphic robot model with different reward imitation ratios, provided sim-to-sim control policy transfer, and compared the gaits in terms of robustness and energy efficiency. In addition, we conducted a qualitative analysis of the gaits by interviewing people, since our task was to create an appealing and natural gait for a humanoid robot. According to the results of the experiments, the most successful approach was the one in which the average value of rewards for imitation and adherence to command velocity per episode remained balanced throughout the training. The gait obtained with this method retains naturalness (median of 3.6 according to the user study) compared to the gait trained with imitation only (median of 4.0), while remaining robust close to the gait trained without reference trajectories., Comment: in Proc. IEEE Int. Conf. on Advanced Robotics (IEEE ICAR 2023). Copyright 20XX IEEE. Personal use of this material is permitted

Superthin galaxies are bulgeless low surface brightness galaxies with unusually high major-to-minor axes ratio of the stellar disc, i.e.,$10

Dwarf galaxies provide a unique opportunity for studying the evolution of the Milky Way (MW) and the Local Group as a whole. Analysing the running solar apex based on the kinematics of the MW satellites, we discovered an unexpected behaviour of the dipole term of the radial velocity distribution as a function of the galactocentric distance. The nearby satellites (<100 kpc) have a bulk motion with an amplitude of 140-230 km/s while the more distant ones show an isotropic distribution of the radial velocities. Such strong solar apex variations can not be explained by the net rotation of the satellites, as it would require an enormously high rotation rate (~970 km/s). If we exclude the LMC and its most closely related members from our sample, this does not suppress the bulk motion of the nearby satellites strongly enough. Nevertheless, we have demonstrated that the observed peculiar kinematics of the MW satellites can be explained by a perturbation caused by the first infall of the LMC. First, we `undone' the effect of the perturbation by integrating the orbits of the MW satellites backwards (forwards) with (without) massive LMC. It appears that the present-day peculiar enhancement of the solar apex in the inner halo is diminished the most in the case of 2x10^{11} Msun LMC. Next, in self-consistent high-resolution N-body simulations of the MW-LMC interaction, we found that the solar apex shows the observed behaviour only for the halo particles with substantial angular momentum, comparable to that of the MW satellites., Comment: 13 pages, 9 figures, accepted for publication in MNRAS

We study two M 51-type systems Arp 68 and Arp 58, which strongly differ by their stellar masses, gas content and environment. Long-slit spectral observations obtained at the 6-m telescope BTA were used to trace the distributions of a line-of-sight (LOS) velocity and a gas-phase oxygen abundance along the spectral cuts. Two systems are compared by their observed properties. We found a very strong large-scale non-circular motion of gas in both systems and a kpc-size saw-edged velocity profile along the tidal spiral arm of Arp 68, probably caused by the gas outflow due to the stellar feedback. A deep decrease of LOS velocity is also found in the `hinge' region in Arp 58, where the inner spiral arm transforms into the tidal spiral arm, which was predicted earlier for M 51-type galaxies. Local sites of star formation and the satellites are compared with the evolutionary models at the colour-colour diagrams. Unlike the spiral galaxy Arp 58, the main galaxy in Arp 68 system is experiencing an ongoing burst of star formation. Gas-phase metallicity estimates show that Arp 58 has a higher metal abundance and reveals a shallow negative radial gradient of the gas-phase oxygen abundance. The emission gas in Arp 68 has noticeably lower metallicity than it is expected for a given luminosity of this galaxy, which may be connected with its space position in the local void., Comment: 13 pages, 15 figures, accepted for publication in MNRAS

Low-mass early-type galaxies, including dwarf spheroidals (dSph) and brighter dwarf ellipticals (dE), dominate the galaxy population in groups and clusters. Recently, an additional early-type population of more extended ultradiffuse galaxies (UDGs) has been identified, sparking a discussion on the potential morphological and evolutionary connections between the three classifications. Here, we present the first measurements of spatially resolved stellar kinematics from deep integrated-light spectra of KDG 64 (UGC 5442), a large dSph galaxy in the M 81 group. From these data, we infer stellar population properties and dark matter halo parameters using Jeans dynamical modelling. We find an old, metal-poor stellar population with no young stars and a dark matter mass fraction of ~ 90 per cent within the half-light radius. These properties and the position of KDG 64 on the Fundamental Plane indicate that it is a local analogue of smaller UDGs in the Coma and Virgo clusters and is probably a transitional dSph-UDG object. Its evolutionary path cannot be uniquely established from the existing data, but we argue that supernovae feedback and tidal heating played key roles in shaping KDG 64., Comment: 10 pages, 5 figures, published in MNRAS

In this work we study the striking case of a narrow blue stream around the NGC 7241 galaxy and its foreground dwarf companion. We want to figure out if the stream was generated by tidal interaction with NGC 7241 or it first interacted with the foreground dwarf companion and later both fell together towards NGC 7241. We use four sets of observations, including a follow-up spectroscopic study with the MEGARA instrument at the 10.4-m Gran Telescopio Canarias. Our data suggest that the compact object we detected in the stream is a foreground Milky Way halo star. Near this compact object we detect emission lines overlapping a bluer and fainter blob of the stream that is clearly visible in both ultra-violet and optical deep images. From its heliocentric systemic radial velocity (Vsyst= 1548.58+/-1.80 km s^-1) and new UV and optical broad-band photometry, we conclude that this over-density could be the actual core of the stream, with an absolute magnitude of M_g ~ -10 and a (g-r) = 0.08 +/- 0.11, consistent with a remnant of a low-mass dwarf satellite undergoing a current episode of star formation. From the width of the stream and assuming a circular orbit, we calculate that the progenitor mass can be the typical of a dwarf galaxy, but it could also be substantially lower if the stream is on a very radial orbit or it was created by tidal interaction with the companion dwarf instead of with NGC 7241. Finally, we find that blue stellar streams containing star formation regions are commonly predicted by high-resolution cosmological simulations of galaxies lighter than the Milky Way. This scenario is consistent with the processes explaining the bursty star formation history of some dwarf satellites, which are followed by a gas depletion and a fast quenching once they enter within the virial radius of their host galaxies for the first time., Comment: 12 pages, 5 figures, accepted for publication in Astronomy & Astrophysics

We present observations and models of the kinematics and distribution of neutral hydrogen (HI) in the superthin galaxy FGC 1440 with an optical axial ratio $a/b = 20.4$. Using the Giant Meterwave Radio telescope (GMRT), we imaged the galaxy with a spectral resolution of 1.7 $\rm kms^{-1}$ and a spatial resolution of $15" \times 13.5"$. We find that FGC 1440 has an asymptotic rotational velocity of 141.8 $\rm kms^{-1}$ . The structure of the HI disc in FGC 1440 is that of a typical thin disc warped along the line of sight, but we can not rule out the presence of a central thick HI disc. We find that the dark matter halo in FGC 1440 could be modeled by a pseudo-isothermal (PIS) profile with $\rm R_{c}/ R_{d} <2$, where $R_{c}$ is the core radius of the PIS halo and $R_{d}$ the exponential stellar disc scale length. We note that in spite of the unusually large axial ratio of FGC 1440, the ratio of the rotational velocity to stellar vertical velocity dispersion, $\frac{V_{Rot}}{\sigma_{z}} \sim 5 - 8$, which is comparable to other superthins. Interestingly, unlike previously studied superthin galaxies which are outliers in the $log_{10}(j_{*}) - log_{10}(M_{*})$ relation for ordinary bulgeless disc galaxies, FGC 1440 is found to comply with the same. The values of $j$ for the stars, gas and the baryons in FGC 1440 are consistent with those of normal spiral galaxies with similar mass., Comment: Accepted for publication in MNRAS

The existence of flat or bulgeless galaxies poses a challenge to the hierarchical structure formation scenario advocated by modern cosmology. We determine the geometrical environment of a sample of $315$ flat galaxies from the Revised Flat Galaxy Catalog (RFGC) using `local dimension' $D$, which, on a given length scale, quantifies the dimension of the cosmic structure in which a galaxy is embedded. For galaxies residing in filaments, nodes and sheets, $D \sim 1$, $D \sim 1.5$ and $D \sim 2$ respectively; $D \sim 3$ represents field galaxies. We also determine the local dimensions of a sample of 15,622 non-flat galaxies identified in the Galaxy Zoo project from the Sloan Digital Sky Survey (SDSS). We find that the median values of $D$ for the flat and the non-flat galaxies are $2.2$ and $1.8$ respectively, implying that flat galaxies are located in a relatively sparser environment compared to non-flat galaxies; a Kolmogorov-Smirnov (KS) test indicates that their geometrical environments are different at $>99$\% confidence level. Further, using a group finding algorithm, we study the local environment of a subset of $779$ flat galaxies with major-to-minor axes ratio $a/b >10$ identified as superthin galaxies. We find that the median clusterization index $k_{\rm{min}}$ for superthin flat galaxies $\sim$ $2.3$ while $\sim$ $1.7$ for other flat galaxies, confirming that the superthins reside in an under-dense environment compared to other flat galaxies at $> 98 \%$ confidence level. Our results may therefore have important implications for the formation and evolution models of flat galaxies in the universe., Comment: 11 pages, 4 figures, 3 tables

In the last years, a new generation of large-scale imaging surveys have probed wide field regions around some nearby galaxies at unprecedented low surface brightness regime (~28.0-29.0 mag arcsec^-2). This offers a chance of discovering very faint dwarf satellites by means of visual inspection of these public deep images. We report the first results of a systematic survey of faint dwarf spheroidal galaxies in the vicinity of the bright late-type spiral NGC 253 galaxy by means of a visual inspection of the images taken by the Dark Energy Survey. Three new dwarf galaxies have been discovered in the vicinity of the brightest member of the Sculptor filament, the late-type spiral NGC 253. Assuming they are companions of NGC 253, their total absolute V-magnitudes fall in the -7 to -9 mag range, which is typical for dwarf satellites in the local Universe. The central surface brightness tend to be extremely low for all the discovered dwarfs and fall roughly in the range of 25-26 mag arcsec^-2 in g-band. Using known data on distances and velocities of galaxies, we estimate the total virial mass of the NGC 253 group to be 8 x 10^11 Mo, which gives the virial radius R_200 = 186 kpc and the turn-around radius of 706 kpc. We also discuss the possible existence of a spatially flattened and velocity-correlated satellite system around NGC 253. This large-scale structure is orientated almost edge-on to line of sight. The possible plane of satellites is only 31 kpc thick with the minor-to-major axis ratio of 0.14. Four out of five galaxies with measured velocities follow a common velocity trend similar to those observed in the planes of satellites around the Andromeda and Centaurus A galaxies. However, the small number of galaxies with known velocities prevents to reach a definitive conclusion about the formation scenario of the structure and its possible relation to the surrounding cosmic web., Comment: 12 pages, 9 figures, 3 tables, accepted for publication in Astronomy & Astrophysics

Mergers and tidal interactions between massive galaxies and their dwarf satellites are a fundamental prediction of the Lambda-Cold Dark Matter cosmology. These events are thought to provide important observational diagnostics of nonlinear structure formation. Stellar streams in the Milky Way and Andromeda are spectacular evidence for ongoing satellite disruption. However, constructing a statistically meaningful sample of tidal streams beyond the Local Group has proven a daunting observational challenge, and the full potential for deepening our understanding of galaxy assembly using stellar streams has yet to be realised. Here we introduce the Stellar Stream Legacy Survey, a systematic imaging survey of tidal features associated with dwarf galaxy accretion around a sample of ~3100 nearby galaxies within z~0.02, including about 940 Milky Way analogues. Our survey exploits public deep imaging data from the DESI Legacy Imaging Surveys, which reach surface brightness as faint as ~29 mag/arcsec^2 in the r band. As a proof of concept of our survey, we report the detection and broad-band photometry of 24 new stellar streams in the local Universe. We discuss how these observations can yield new constraints on galaxy formation theory through comparison to mock observations from cosmological galaxy simulations. These tests will probe the present-day mass assembly rate of galaxies, the stellar populations and orbits of satellites, the growth of stellar halos and the resilience of stellar disks to satellite bombardment., Comment: Accepted in Astronomy & Astrophysics, 25 pages, 17 figures, 3 tables

The Extragalactic Distance Database (EDD) was created as a repository for high quality, redshift-independent distances. A key component of EDD is the Color Magnitude Diagrams/Tip of the Red Giant Branch (CMDs/TRGB) catalog, which provides information on the stellar content of nearby galaxies observed with the Hubble Space Telescope (HST). Here we provide a decadal update to this catalog, which has now doubled in size to over 500 galaxies. We highlight the additions to our data reduction and analysis techniques, and provide examples of the science that has been made possible with this large data set. We find the TRGB to be a reliable measure for distance, and we aim to extend its distance coverage with HST to every galaxy within 10 Mpc. In the near-future, the combination of the James Webb Space Telescope and the Nancy Grace Roman Space Telescope will dramatically increase the number of targets within our grasp., Comment: 8 figures, 20 pages. Accepted to AJ. Materials available at edd.ifa.hawaii.edu

Hong-Ou-Mandel (HOM) effect is known to be one of the main phenomena in quantum optics. The effect occurs when two identical single-photon waves enter a 1:1 beam splitter, one in each input port. When the photons are identical, they will extinguish each other. One of the main elements of the HOM interferometer is the beam splitter, which has its own coefficients of reflection $R = 1/2$ and transmission $ T = 1/2 $. In this work, the general mechanism of the interaction of two photons in a beam splitter is considered using an analytical solution, which shows that in the HOM theory of the effect it is necessary to know (including when planning the experiment) not only $ R = 1/2 $ and $ T = 1/2 $, but also their root-mean-square fluctuations $ \Delta R ^ 2, \Delta T ^ 2 $, which arise due to the dependence of $R = R(\omega_1, \omega_2) $ and $ T = T (\omega_1, \omega_2) $ on the frequencies where $\omega_1, \omega_2$ are the frequencies of the first and second photons, respectively. Under certain conditions, specifically when the dependence of the fluctuations $ \Delta R^2 $ and $ \Delta T^2 $ can be neglected and $ R=T=1/2 $ is chosen, the developed theory coincides with previously known results.

We study the navigation problem for a robot moving amidst static and dynamic obstacles and rely on a hierarchical approach to solve it. First, the reference trajectory is planned by the safe interval path planning algorithm that is capable of handling any-angle translations and rotations. Second, the path following problem is treated as the constrained control problem and the original flatness-based approach is proposed to generate control. We suggest a few enhancements for the path planning algorithm aimed at finding trajectories that are more likely to be followed by a robot without collisions. Results of the conducted experimental evaluation show that the number of successfully solved navigation instances significantly increases when using the suggested techniques., Comment: Camera-ready version of the paper as submitted to ICR'19

We theoretically analyze the quantum vortices - the zeros of electron wave function which are formed through atom ionization by ultrashort laser pulse. In 2D space we consider the case of above-threshold ionization of hydrogen atom and in 3D space the ionization of the atom in the zero-radius-potential approximation. With the help of obtained analytical results we make the assumption that localization of quantum vortices in 3D space can be predicted by analysis of 2D model.

One of the most effective methods for cooling micro and nano devices to ultra low temperatures is the sideband method. Currently, this approach is being studied experimentally and theoretically. Theoretical results that relate to this method correspond to the case of the interaction of an electromagnetic field with a micro or nano resonator through radiation pressure. Obviously, if you choose a charged micro or nano resonator, the interaction will be different. In this paper, this case is considered and it is shown that cooling will be as effective as in the sideband method. The resulting final equation in the work, for the average value of the quantum number of the cooled resonator, has a surprisingly simple analytical form, which allows for the most complete analysis of the system under study.

It is of broad interest for galaxy formation theory to carry out a full inventory of the numbers and properties of dwarf galaxies in the Local Volume, both satellites and isolated ones. Ultra-deep imaging in wide areas of the sky with small amateur telescopes can help to complete the census of these hitherto unknown low surface brightness galaxies, which cannot be detected by the current resolved stellar population and HI surveys. We report the discovery of Donatiello I, a dwarf spheroidal galaxy located one degree from the star Mirach (Beta And) in a deep image taken with an amateur telescope. The color--magnitude diagram obtained from follow-up observations obtained with the Gran Telescopio Canarias (La Palma, Spain) reveals that this system is beyond the Local Group and is mainly composed of old stars. The absence of young stars and HI emission in the ALFALFA survey are typical of quenched dwarf galaxies. Our photometry suggests a distance modulus for this galaxy of (m-M)=27.6 +/- 0.2 (3.3 Mpc), although this distance cannot yet be established securely owing to the crowding effects in our color--magnitude diagram. At this distance, Donatiello I's absolute magnitude (M_v =-8.3), surface brightness (mu_v=26.5 mag arcsec^-2) and stellar content are similar to the "classical" Milky Way companions Draco or Ursa Minor. The projected position and distance of Donatiello I are consistent with being a dwarf satellite of the closest S0-type galaxy NGC 404 ("Mirach's Ghost"). Alternatively, it could be one of the most isolated quenched dwarf galaxies reported so far behind the Andromeda galaxy., Comment: 11 pages, 8 figures, accepted for publication in Astronomy & Astrophysics

We present high resolution H{\sc i} 21cm Giant Meterwave Radio Telescope (GMRT) observations of the superthin galaxy FGC1540 with a spatial resolution of 10$''$ $\times$ 8$''$ and a spectral resolution of 1.73 kms$^{-1}$ and an rms noise of 0.9 mJy per beam. We obtain its rotation curve as well as deprojected radial H{\sc i} surface density profile by fitting a 3-dimensional tilted ring model directly to the H{\sc i} data cubes by using the publicly-available software, Fully Automated Tirrific (FAT). We also present the rotation curve of FGC1540 derived from its optical spectroscopy study using the 6-m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We use the rotation curve, the H{\sc i} surface density profile together with Spitzer 3.6 $\mu$m and the SDSS $i$--band data to construct the mass models for FGC1540. We find that both the Pseudo-isothermal (PIS), as well as Navarro-Frenk-White (NFW) dark matter (DM) halos, fit the observed rotation curve equally well. The PIS model indicates a compact dark matter halo ($R_{\rm C}/R_{\rm D}$ < 2), with the best-fitting core radius ($R_{\rm C}$) approximately half the exponential stellar disc scale length ($R_{\rm D}$), which is in agreement with the mass models of superthin galaxies studied earlier in the literature. Since the vertical thickness of the galactic stellar disc is determined by a balance between the net gravitational field and the velocity dispersion in the vertical direction, the compact dark matter halo may be primarily responsible in regulating the superthin vertical structure of the stellar disc in FGC1540 as was found in case of the superthin galaxy UGC7321., Comment: Accepted for publication in MNRAS

If the extremely low surface brightness galaxy Coma P lies at $5.5\pm0.3$ Mpc as recently proposed then it would have an extraordinarily deviant peculiar velocity of $\sim900$ km $\mathrm{s^{-1}}$ at a location where differential velocities between galaxies are low. We have accessed the images from the HST archives used to derive the literature distance from the magnitude of the tip of the red giant branch. Our analysis gives the distance to be $10.9\pm1.0$ Mpc. At this location the galaxy lies within the infall region of the Virgo Cluster, such that its still considerable peculiar velocity of $\sim500$ km $\mathrm{s^{-1}}$ is consistent with an established model. Coma P has an unusually pronounced asymptotic giant branch relative to its red giant branch. The dominant stellar population is just a few Gyr old., Comment: Accepted for publication in ApJL, 7 pages, 3 figures

A system of two coupled quantum harmonic oscillators with the Hamiltonian ${\hat H}=\frac{1}{2}\left(\frac{1}{m_1}{\hat p}^{2}_1 + \frac{1}{m_2}{\hat p}^{2}_2+A x^2_1+B x^2_2+ C x_1 x_2\right)$ can be found in many applications of quantum and nonlinear physics, molecular chemistry, and biophysics. The stationary wave function of such a system is known, but its use for the analysis of quantum entanglement is complicated because of the complexity of computing the Schmidt modes. Moreover, there is no exact analytical solution to the nonstationary Schrodinger equation ${\hat H}\Psi=i\hbar\frac{\partial \Psi}{\partial t}$ and Schmidt modes for such a dynamic system. In this paper we find a solution to the nonstationary Schrodinger equation; we also find in an analytical form a solution to the Schmidt mode for both stationary and dynamic problems. On the basis of the Schmidt modes, the quantum entanglement of the system under consideration is analyzed. It is shown that for certain parameters of the system, quantum entanglement can be very large.

At present, there are many methods of quantum entanglement of particles with an electromagnetic field. Most methods have a low probability of quantum entanglement and not an exact theoretical apparatus based on an approximate solution of the Schrodinger equation. There is a need for new methods for obtaining quantum-entangled particles and mathematically accurate studies of such methods. In this paper, a quantum harmonic oscillator (for example, an electron in a magnetic field) interacting with a quantized electromagnetic field is considered. Based on the exact solution of the Schrodinger equation for this system, it is shown that for certain parameters there can be a large quantum entanglement between the electron and the electromagnetic field. Quantum entanglement is analyzed on the basis of a mathematically exact expression for the Schmidt modes and the Von Neumann entropy.