Astrophysics of Galaxies (astro-ph.GA)

Abstract: Previous results suggest that there exists a correlation between the size of the bulge of a galaxy and the number of its dwarf galaxy satellites. This was found to be inconsistent with the standard model of cosmology based on comparisons to semi-analytical dark matter-only simulations, where no such correlation was found. In this work, we extend these studies using the volume-complete ELVES dwarf galaxy catalog, which increases the number of systems compared to previous work by a factor of four. For each giant galaxy we compile the bulge-to-total baryonic mass (B/T) ratio and put it as a function of the number of dwarf galaxies surrounding them within 250 kpc (N$_{250}$). For the 29 galaxy systems in the ELVES catalog, we find a linear relation between B/T and N$_{250}$ which is consistent with previous data. However, for a given stellar mass of the host galaxy this relation is mainly driven by their morphology, where early-type galaxies have a larger B/T ratio and a larger N$_{250}$ than late type galaxies. By investigating spiral galaxies in Illustris-TNG100, we tested whether the inclusion of baryons in the simulations will change the results based on Millennium-II. Contrary to dark matter-only simulations, we do find a correlation between B/T and N$_{250}$, indicating that the standard model of cosmology does predict a correlation. The empirical relation between the number of satellites and the bulge to total stellar mass is therefore not necessarily in tension with $\Lambda$CDM.

Abstract: In the manuscript, a candidate of sub-pc binary black hole (BBH) system is reported in SDSS J1257+2023 through different properties of broad Balmer emission lines. After subtractions of host galaxy contributions, Gaussian functions are applied to measure emission lines in SDSS J1257+2023, leading line width (second moment) 760${\rm km/s}$ of broad H$\beta$ to be 0.69 times of line width 1100${\rm km/s}$ of broad H$\alpha$, quite different from normal line width ratio 1.1 of broad H$\beta$ to broad H$\alpha$ in quasars. The quite broader component in broad H$\alpha$ in SDSS J1257+2023 can be confirmed with confidence level higher than $5\sigma$ through F-test technique, through different model functions applied to measure emission lines. The broad Balmer emission lines having different line widths can be naturally explained by a BBH system with different obscurations on central two independent BLRs. Meanwhile, through ZTF light curves and corresponding phase folded light curves well described by sinusoidal function, BBH system expected optical QPOs can be detected with periodicity about 1000days, confirmed with confidence level higher than $3\sigma$ by Generalized Lomb-Scargle periodogram. And through CAR process simulated light curves, confidence level higher than $2\sigma$ can be determined to support the optical QPOs in SDSS J1257+2023 not from intrinsic AGN activities, although the ZTF light curves have short time durations. Moreover, through oversimplified BBH system simulated results, studying different broad Balmer lines as signs of BBH systems in normal quasars with flux ratios around 4 of broad H$\alpha$ to broad H$\beta$ could be done in near future.

Abstract: We report the first laboratory and interstellar detection of the alpha-cyano vinyl radical (H2CCCN). This species was produced in the laboratory by an electric discharge of a gas mixture of vinyl cyanide, CH2CHCN, and Ne, and its rotational spectrum was characterized using a Balle-Flygare narrowband-type Fourier-transform microwave spectrometer operating in the frequency region of 8-40 GHz. The observed spectrum shows a complex structure due to tunneling splittings between two torsional sublevels of the ground vibronic state, 0+ and 0-, derived from a large-amplitude inversion motion. In addition, the presence of two equivalent hydrogen nuclei makes necessary to discern between ortho- and para-H2CCCN. A least squares analysis reproduces the observed transition frequencies with a standard deviation of ca. 3 kHz. Using the laboratory predictions, this radical is detected in the cold dark cloud TMC-1 using the Yebes 40m telescope and the QUIJOTE line survey. The 404-303 and 505-404 rotational transitions, composed of several hyperfine components, were observed in the 31.0-50.4 GHz range. Adopting a rotational temperature of 6K we derive a column density of (1.4+/-0.2)e11 cm-2 and (1.1+/-0.2)e11 cm-2 for ortho-H2CCCN and para-H2CCCN, respectively. The reactions C + CH3CN, and perhaps also N + CH2CCH, emerge as the most likely routes to H2CCCN in TMC-1.

Abstract: The relation between the resolved star formation rate per unit area and the non-thermal radio continuum emission is studied in 21 Virgo cluster galaxies and the two nearby spiral galaxies, NGC6946 and M51. For the interpretation and understanding of our results we used a 3D model where star formation, 2D cosmic ray (CR) propagation, and the physics of synchrotron emission are included. Based on the linear correlation between the star formation rate per unit area and the synchrotron emission and its scatter radio-bright and radio-dim regions can be robustly defined for our sample of spiral galaxies. We identified CR diffusion or streaming as the physical causes of radio-bright regions of unperturbed symmetric spiral galaxies as NGC6946. We identified the probable causes of radio-bright regions in several galaxies as CR transport, via either gravitational tides (M51) or galactic winds (NGC4532) or ram pressure stripping (NGC4330 and NGC4522). Three galaxies are overall radio-dim: NGC4298, NGC4535, and NGC4567. Based on our model of synchrotron-emitting disks we suggest that the overall radio-dim galaxies have a significantly lower magnetic field than expected by equipartition between the magnetic and turbulent energy densities. Radio-bright regions frequently coincide with asymmetric ridges of polarized radio continuum emission, and we found a clear albeit moderate correlation between the polarized radio continuum emission and the radio/SFR ratio. When compression or shear motions of the interstellar medium (ISM) are present in the galactic disk, the radio-bright regions are linked to the commonly observed asymmetric ridges of polarized radio continuum emission and represent a useful tool for the interaction diagnostics. Based on our results, we propose a scenario for the interplay between star formation, CR electrons, and magnetic fields in spiral galaxies.

Abstract: We present high-resolution VLT/UVES spectroscopy and a detailed analysis of the unique Broad Absorption-Line system towards the quasar SDSS J165252.67+265001.96. This system exhibits low-ionization metal absorption lines from the ground states and excited energy levels of Fe II and Mn II, and the meta-stable 2^3S excited state of He I. The extended kinematics of the absorber encompasses three main clumps with velocity offsets of -5680, -4550, and -1770 km s$^{-1}$ from the quasar emission redshift, $z=0.3509\pm0.0003$, derived from [O II] emission. Each clump shows moderate partial covering of the background continuum source, $C_f \approx [0.53; 0.24; 0.81]$. We discuss the excitation mechanisms at play in the gas, which we use to constrain the distance of the clouds from the Active Galactic Nucleus (AGN) as well as the density, temperature, and typical sizes of the clouds. The number density is found to be $n_{\rm H} \sim 10^4\rm cm^{-3}$ and the temperature $T_e \sim 10^4\rm\,K$, with longitudinal cloudlet sizes of $\gtrsim0.01$ pc. Cloudy photo-ionization modelling of He I$^{*}$, which is also produced at the interface between the neutral and ionized phases, assuming the number densities derived from Fe II, constrains the ionization parameter to be $\log U \sim -3$. This corresponds to distances of a few 100 pc from the AGN. We discuss these results in the more general context of associated absorption-line systems and propose a connection between FeLoBALs and the recently-identified molecular-rich intrinsic absorbers. Studies of significant samples of FeLoBALs, even though rare per se, will soon be possible thanks to large dedicated surveys paired with high-resolution spectroscopic follow-ups.