Astrophysics

Most active supermassive black holes (SMBH) in present-day galaxies are underfed and consist of low-luminosity active galactic nuclei (LLAGN). They have multiwavelength broadband spectral energy distributions (SED) dominated by non-thermal processes which are quite different from those of the brighter, more distant quasars. Modelling the observed SEDs of LLAGNs is currently challenging, given the large computational expenses required. In this work, we used machine learning (ML) methods to generate model SEDs and fit sparse observations of LLAGNs. Our ML model consisted of a neural network and reproduced with excellent precision the radio-to-X-rays emission from a radiatively inefficient accretion flow around a SMBH and a relativistic jet, at a small fraction of the computational cost. The ML method performs the fit 4? 10 5 times faster than previous semianalytic models. As a proof-of-concept, we used the ML model to reproduce the SEDs of the LLAGNs M87, NGC 315 and NGC 4261.

We report the detection of [O I]145.5um in the BR 1202-0725 system, a compact group at z=4.7 consisting of a quasar (QSO), a submillimeter-bright galaxy (SMG), and three faint Lya emitters. By taking into account the previous detections and upper limits, the [O I]/[C II] line ratios of the now five known high-z galaxies are higher than or on the high-end of the observed values in local galaxies ([O I]/[C II] ??0.13). The high [O I]/[C II] ratios and the joint analysis with the previous detection of [N II] lines for both the QSO and the SMG suggest the presence of warm and dense neutral gas in these highly star-forming galaxies. This is further supported by new CO (12-11) line detections and a comparison with cosmological simulations. There is a possible positive correlation between the [NII]122/205 line ratio and the [O I]/[C II] ratio when all local and high-z sources are taken into account, indicating that the denser the ionized gas, the denser and warmer the neutral gas (or vice versa). The detection of the [O I] line in the BR1202-0725 system with a relatively short amount of integration with ALMA demonstrates the great potential of this line as a dense gas tracer for high-z galaxies.

BOSS-EUVLG1 is the most ultraviolet (UV) and Ly α luminous galaxy detected so far in the Universe, going through a very active starburst phase, and forming stars at a rate (SFR) of 955 ± 118 M ??yr ?? . We report the detection of a broad H α component carrying 25% of the total H α flux. The broad H α line traces a fast and massive ionized gas outflow characterized by a total mass, log( M out [ M ??]), of 7.94 ± 0.15, an outflowing velocity (V out ) of 573 ± 151 km s ?? , and an outflowing mass rate ( M ? out ) of 44 ± 20 M ??yr ?? . The presence of the outflow in BOSS-EUVLG1 is also supported by the identification of blueshifted UV absorption lines in low and high ionization states. The energy involved in the H α outflow can be explained by the ongoing star formation without the need for an Active Galactic Nucleus. The derived low mass loading factor ( η = 0.05 ± 0.03) indicates that although massive, this phase of the outflow can not be relevant for the quenching of the star formation. In addition, only a small fraction ( ??15%) of the ionized outflowing material with velocities above 372 km s ?? could escape the gravitational potential, and enrich the surrounding circum-galactic medium at distances above tens of kpc. The ionized phase of the outflow does not carry the mass and energy to play a relevant role neither in the evolution of the host galaxy nor in the enrichment of the intergalactic medium. Other phases of the outflow could be carrying most of the outflow energy and mass in the form of hot X-ray emitting gas as predicted by some recent simulations. The expected emission of the extended X-ray emitting halo associated with the outflow in BOSS-EUVLG1 and similar galaxies could be detected with the future X-ray observatory, {\it ATHENA} but could not be resolved spatially.

The sedimentation level of blue straggler stars (BSS) has been shown to be a great tool to investigate the dynamical states of globular clusters (GCs). The area enclosed between the cumulative radial distributions of BSS and a reference population up to the half-mass radius of the clusters, A + rh , is known to be a measure of the sedimentation of BSS in GCs. In this work, we calculate A + rh for 12 open clusters (OCs) using main-sequence turn-off stars as a reference population. The BSS as well as the main-sequence turn-off stars for these clusters are identified using the proper motions and parallaxes from the Gaia DR2 data, with spectroscopically confirmed BSS populations for some of these clusters available in the literature. Using the Pearson and Spearman rank correlation coefficients, we find weak correlations between the estimated values of A + rh and other markers of dynamical ages of the clusters, i.e., the number of central relaxations a cluster has experienced since its formation, and the structural parameters of the clusters. Based on statistical tests, we find that these correlations are similar to the corresponding correlations among the less evolved GCs, albeit within large errors.

We study, for the first time, the relations of two strong diffuse bands (DIBs) at 9633 and 9577~?, commonly attributed to C + 60 , to other interstellar features seen in optical and UV spectra including H{\sc i}, Ca{\sc i}, Fe{\sc ii}, Na{\sc i}, Ti{\sc ii}, CN, CH, CH + , and C 2 and DIBs 5780, 5797, 6196, 6269, 6284, and 6614. We analyzed 62 lines of sight where the stellar contamination by Mg{\sc ii} was corrected or found negligible for DIB 9633. Equivalent widths of DIB 9577 were measured in 62 lines of sight. Poor mutual correlation between the strengths of the above features and the major diffuse bands (5780 and 5797) as well as with other DIBs (with some exceptions) were revealed. The considered DIBs are also poorly correlated with the features of neutral hydrogen, molecular carbon, and those of simple interstellar radicals. Perhaps this phenomenon can be explained if the diffuse band 9577 is an unresolved blend of two or more interstellar features. There are indications that 9633 and 9577 diffuse bands are stronger in ? -type clouds, i.e. these features resemble the behavior of reasonably broad DIBs, which are strong in the lines of sight where the UV flux from the very hot nearby stars plays an important role.

We observed the high-mass star-forming region G335.579-0.292 with the Atacama Large Millimeter/submillimeter Array (ALMA) at 226 GHz with an angular resolution of 0.3'' ( ??000 au resolution at the source distance). G335.579-0.292 hosts one of the most massive cores in the Galaxy (G335-MM1). The continuum emission shows that G335-MM1 fragments into at least five sources, while molecular line emission is detected in two of the continuum sources (ALMA1 and ALMA3). We found evidence of large and small scale infall in ALMA1 revealed by an inverse P-Cygni profile and the presence of a blue-shifted spot at the center of the first moment map of the CH 3 CN emission. In addition, hot gas expansion in the innermost region is unveiled by a red-shifted spot in the first moment map of HDCO and (CH 3 ) 2 CO (both with E u >1100 K). Our modeling reveals that this expansion motion originates close to the central source, likely due to reversal of the accretion flow induced by the expansion of the HII region, while infall and rotation motions originate in the outer regions. ALMA3 shows clear signs of rotation, with a rotation axis inclination with respect to the line of sight close to 90 ??, and a system mass (disk + star) in the range of 10-30 M ??.

We present the discovery in TMC-1 of vinyl acetylene, CH2CHCCH, and the detection, for the first time in a cold dark cloud, of HCCN, HC4N, and CH3CH2CN. A tentative detection of CH3CH2CCH is also reported. The column density of vinyl acetylene is (1.2 +/- 0.2)e13 cm-2, which makes it one of the most abundant closed-shell hydrocarbons detected in TMC-1. Its abundance is only three times lower than that of propylene, CH3CHCH2. The column densities derived for HCCN and HC4N are (4.4 +/- 0.4)e11 cm-2 and (3.7 +/- 0.4)e11 cm-2, respectively. Hence, the HCCN/HC4N abundance ratio is 1.2 +/- 0.3. For ethyl cyanide we derive a column density of (1.1 +/- 0.3)e11 cm-2. These results are compared with a state-of-the-art chemical model of TMC-1, which is able to account for the observed abundances of these molecules through gas-phase chemical routes.

We present the first set of cosmological baryonic zoom-in simulations of galaxies including dissipative self-interacting dark matter (dSIDM). These simulations utilize the Feedback In Realistic Environments (FIRE-2) galaxy formation physics, but allow the dark matter to have dissipative self-interactions analogous to Standard Model forces, parameterized by the self-interaction cross-section per unit mass, (?/m) , and the dimensionless degree of dissipation, 0< f diss <1 . We survey this parameter space, including constant and velocity-dependent cross-sections, and focus on structural and kinematic properties of dwarf galaxies with M halo ??10 10??1 M ??. Central density profiles of simulated dwarfs become cuspy when (?/m ) eff ??.1c m 2 g ?? (and f diss =0.5 as fiducial). The power-law slopes asymptote to ��?1.5 in low-mass dwarfs independent of cross-section, which arises from a dark matter ``cooling flow''. Through comparisons with dark matter only simulations, we find the profile in this regime is insensitive to the inclusion of baryons. However, when (?/m ) eff ??.1c m 2 g ?? , baryonic effects can produce cored density profiles comparable to non-dissipative cold dark matter (CDM) runs but at smaller radii. Simulated galaxies with (?/m)??0c m 2 g ?? develop significant coherent rotation of dark matter, accompanied by halo deformation, but this is unlike the well-defined thin ``dark disks'' often attributed to baryon-like dSIDM. The density profiles in this high cross-section model exhibit lower normalizations given the onset of halo deformation. For our surveyed dSIDM parameters, halo masses and galaxy stellar masses do not show appreciable difference from CDM, but dark matter kinematics and halo concentrations/shapes can differ.

Two dwarf galaxies: WOC2017-07 and PGC 704814 located in the vicinity of the nearby luminous spiral galaxy NGC 253 were observed with the Advanced Camera for Surveys on the Hubble Space Telescope. Their distances of 3.62 ± 0.18 Mpc and 3.66 ± 0.18 Mpc were derived using the tip of the red giant branch method. These distances are consistent with the dwarf galaxies being members of the NGC 253 group. Based on the radial velocities and projected separations of seven assumed dwarf companions, we estimated the total mass of NGC 253 to be (8.1±2.6) 10 11 M ??, giving a total-mass-to- K -luminosity ratio M orb / L K =(8.5±2.7) M ??/ L ??. A notable property of NGC 253 is its declined rotation curve. NGC 253 joins four other luminous spiral galaxies in the Local Volume with declined rotation curves (NGC 2683, NGC 2903, NGC 3521 and NGC 5055) that together have the low average total-mass-to-luminosity ratio, M orb / L K =(5.5±1.1) M ??/ L ??. This value is only ??1/5 of the corresponding ratio for the Milky Way and M 31.

Radio relics are elongated sources related to shocks driven by galaxy cluster merger events. Although these objects are highly polarized at GHz frequencies ( ??0% ), high-resolution studies of their polarization properties are still lacking. We present the first high-resolution and high-sensitivity polarimetry study of the merging galaxy cluster CIZA J2242.8+5301 in the 1-4 GHz frequency band. We use the QU -fitting approach to model the Stokes I , Q and U emission, obtaining best-fit intrinsic polarization fraction ( p 0 ), intrinsic polarization angle ( ? 0 ), Rotation Measure (RM) and wavelength-dependent depolarization ( ? RM ) maps of the cluster. Our analysis focuses on the northern relic (RN). For the first time in a radio relic, we observe a decreasing polarization fraction in the downstream region. Our findings are possibly explained by geometrical projections and/or by decreasing of the magnetic field anisotropy towards the cluster center. From the amount of depolarization of the only detected background radio galaxy, we estimate a turbulent magnetic field strength of B turb ??.6 μ Gauss in the relic. Finally, we observe Rotation Measure fluctuations of about 30 rad m ?? around at the median value of 140.8 rad m ?? at the relic position.