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We present a study of low surface brightness galaxies (LSBGs) selected by fitting the images for all the galaxies in $\alpha$.40 SDSS DR7 sample with two kinds of single-component models and two kinds of two-component models (disk+bulge): single exponential, single s\'{e}rsic, exponential+deVaucular (exp+deV), and exponential+s\'{e}rsic (exp+ser). Under the criteria of the B band disk central surface brightness $\mu_{\rm 0,disk}{\rm (B) \geqslant 22.5\ mag\ arcsec^{-2}}$ and the axis ratio $\rm b/a > 0.3$, we selected four none-edge-on LSBG samples from each of the models which contain 1105, 1038, 207, and 75 galaxies, respectively. There are 756 galaxies in common between LSBGs selected by exponential and s\'{e}rsic models, corresponding to 68.42% of LSBGs selected by the exponential model and 72.83% of LSBGs selected by the s\'{e}rsic model, the rest of the discrepancy is due to the difference in obtaining $\mu_{0}$ between the exponential and s\'{e}rsic models. Based on the fitting, in the range of $0.5 \leqslant n \leqslant 1.5$, the relation of $\mu_{0}$ from two models can be written as $\mu_{\rm 0,s\acute{e}rsic} - \mu_{\rm 0,exp} = -1.34(n-1)$. The LSBGs selected by disk+bulge models (LSBG_2comps) are more massive than LSBGs selected by single-component models (LSBG_1comp), and also show a larger disk component. Though the bulges in the majority of our LSBG_2comps are not prominent, more than 60% of our LSBG_2comps will not be selected if we adopt a single-component model only. We also identified 31 giant low surface brightness galaxies (gLSBGs) from LSBG_2comps. They are located at the same region in the color-magnitude diagram as other gLSBGs. After we compared different criteria of gLSBGs selection, we find that for gas-rich LSBGs, $M_{\star} > 10^{10}M_{\odot}$ is the best to distinguish between gLSBGs and normal LSBGs with bulge., Comment: 21 pages, 10 figures, 6 tables, accepted by Research in Astronomy and Astrophysics

Ionization sources other than HII regions give rise to the right-hand branch in the standard ([NII]) BPT diagram, populated by Seyfert 2s and LINERs. However, because the majority of Seyfert/LINER hosts are star forming (SF), HII regions contaminate the observed lines to some extent, making it unclear if the position along the branch is merely due to various degrees of mixing between pure Seyfert/LINER and SF, or whether it reflects the intrinsic diversity of Seyfert/LINER ionizing sources. In this study, we empirically remove SF contributions in ~100,000 Seyfert/LINERs from SDSS using the doppelganger method. We find that mixing is not the principal cause of the extended morphology of the observed branch. Rather, Seyferts/LINERs intrinsically have a wide range of line ratios. Variations in ionization parameter and metallicity can account for much of the diversity of Seyfert/LINER line ratios, but the hardness of ionization field also varies significantly. Furthermore, our k-means classification on seven decontaminated emission lines reveals that LINERs are made up of two populations, which we call soft and hard LINERs. The Seyfert 2s differ from both types of LINERs primarily by higher ionization parameter, whereas the two LINER types mainly differ from each other (and from star-forming regions) in the hardness of the radiation field. We confirm that the [NII] BPT diagram more efficiently identifies LINERs than [SII] and [OI] diagnostics, because in the latter many LINERs, especially soft ones, occupy the same location as pure star-formers, even after the SF has been removed from LINER emission., Comment: Accepted to ApJ. Main results in Figures 6 and 7. Seyfert/LINER classification (Table 1) available at https://salims.pages.iu.edu/agn . Comments welcome

It was found that spatially confined spin-orbit (SO) coupling, which can be induced by illuminating Bose-Einstein condensates (BECs) with a Gaussian laser beam, can help trap a spinor Bose gas in multi-dimensional space. Previous works on this topic were all based on a Boson gas featuring an attractive interaction. In this paper, we consider the trapping effect in the case in which the Boson gas features a repulsive interaction. After replacing the repulsive effect, stable excited modes of semi-vortex (SV) type and mixed-mode (MM) type, which cannot be created in a boson gas with attractive interactions, can be found in the current setting. The trapping ability and the capacity of the confined SO coupling versus the degree of the repulsive strength as well as the order of the excited mode are systematically discussed firstly through the paper. Moreover, the stability of the nonlinear mode trapped in this system with a moving reference frame is also discussed. Unlike the system with homogeneous SO coupling, two different types of stationary mobility modes can be stabilized when the SO coupling moves in the x- and y- directions, respectively. This finding indicates that the system with moving confined SO coupling features a typical anisotropic character that differs from the system with moving homogeneous SO coupling., Comment: 11 pages, 5 figures,to be published in Nonlinear Dynamics

Low-surface-brightness galaxies(LSBGs) are defined as galaxies that are fainter than dark night sky and are important for studying our universe. Particularly, edge-on galaxies are useful for the study of rotational velocity and dynamical properties of galaxies. Hence here we focus on searching for edge-on LSBGs. In order to find these edge-on dim galaxies, a series of effects caused by inclination, including the surface brightness profile, internal extinction, and scale length, have been corrected. In this work, we present a catalog of 281 edge-on LSBG candidates, which are selected from the cross-match between SDSS DR7 and the 40% ALFALFA catalog. We also present the properties of these edge-on LSBG candidates including absolute magnitude, central surface brightness, B-V color, scale length, and relative thickness. Our result suggests that the correction of inclination effects is very important for obtaining a complete sample of LSBGs., Comment: 14 pages, 7 figures, 2 tables

Ultra-diffuse galaxies (UDGs) are objects which have very extended morphology and faint central surface brightness. Most UDGs are discovered in galaxy clusters and groups, but also some are found in low density environments. The diffuse morphology and faint surface brightness make them difficult to distinguish from the sky background. Several previous works have suggested that at least some UDGs are consistent with exponential surface brightness profiles (S\'{e}rsic n ~ 1). The surface brightness of exponential disks is enhanced in edge-on systems, so searching for edge-on systems may be an efficient way to select UDGs. In this paper, we focus on searching for edge-on HI-bearing ultra-diffuse sources (HUDS) from the 40% ALFALFA catalog, based on SDSS g- and r-band images. After correcting the observed central surface brightness to a face-on perspective, we discover 11 edge-on HUDS candidates. All these newly discovered HUDS candidates are blue and HI-bearing, similar to other HUDS in 70% ALFALFA catalog, and different from UDGs in clusters., Comment: 13 Pages, 5 figures

We present a narrow $\rm H\alpha$-band imaging survey of 357 low surface brightness galaxies (LSBGs) that are selected from the spring sky region of the 40% Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) HI Survey. All the $\rm H\alpha$ images are obtained from the 2.16 m telescope, operated by Xinglong Observatory of the National Astronomical Observatories, Chinese Academy of Sciences. We provide the $\rm H\alpha$ fluxes and derive the global star formation rates (SFRs) of LSBGs after the Galactic extinction, internal extinction, and [NII] contamination correction. Comparing to normal star-forming galaxies, LSBGs have a similar distribution in the HI surface density ($\rm \Sigma_{HI}$), but their SFRs and star formation surface density ($\rm \Sigma_{SFR}$) are much lower. Our results show that the gas-rich LSBGs selected from the ALFALFA survey obviously deviate from the Kennicutt-Schmidt law, in the relation between the star formation surface density ($\rm \Sigma_{SFR}$) and the gas surface density ($\rm \Sigma_{gas}$). However, they follow the extended Schmidt law well when taking the stellar mass of the galaxy into consideration., Comment: 17 pages, 11 figures

We present a spectroscopic redshift catalog from the LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) in the Southern Galactic Cap (SGC), which is designed to observe all sources (Galactic and extra-galactic) by using repeating observations with a limiting magnitude of $r=18.1~mag$ in two $20~deg^2$ fields. The project is mainly focusing on the completeness of LAMOST ExtraGAlactic Surveys (LEGAS) in the SGC, the deficiencies of source selection methods and the basic performance parameters of LAMOST telescope. In both fields, more than 95% of galaxies have been observed. A post-processing has been applied to LAMOST 1D spectrum to remove the majority of remaining sky background residuals. More than 10,000 spectra have been visually inspected to measure the redshift by using combinations of different emission/absorption features with uncertainty of $\sigma_{z}/(1+z)<0.001$. In total, there are 1528 redshifts (623 absorption and 905 emission line galaxies) in Field A and 1570 redshifts (569 absorption and 1001 emission line galaxies) in Field B have been measured. The results show that it is possible to derive redshift from low SNR galaxies with our post-processing and visual inspection. Our analysis also indicates that up to 1/4 of the input targets for a typical extra-galactic spectroscopic survey might be unreliable. The multi-wavelength data analysis shows that the majority of mid-infrared-detected absorption (91.3%) and emission line galaxies (93.3%) can be well separated by an empirical criterion of $W2-W3=2.4$. Meanwhile, a fainter sequence paralleled to the main population of galaxies has been witnessed both in $M_r$/$W2-W3$ and $M_*$/$W2-W3$ diagrams, which could be the population of luminous dwarf galaxies but contaminated by the edge-on/highly inclined galaxies ($\sim30\%$)., Comment: 19 pages, 14 figures, 2 MRT, accepted by ApJS