Astrophysics of Galaxies (astro-ph.GA)

Abstract: Black hole driven outfBlack hole driven outflows in galaxies hosting active galactic nuclei (AGN) may interact with their interstellar medium (ISM) affecting star formation. Such feedback processes, reminiscent of those seen in massive galaxies, have been reported recently in some dwarf galaxies. However, such studies have usually been on kiloparsec and larger scales and our knowledge on the smallest spatial scales to which this feedback processes can operate is unclear. Here we demonstrate radio jet-ISM interaction on the scale of an asymmetric triple radio structure of $\sim$10 parsec size in NGC 4395. This triplet radio structure is seen in the 15 GHz continuum image and the two asymmetric jet like structures are situated on either side of the radio core that coincides with the optical {\it Gaia} position. The high resolution radio image and the extended [OIII]$\lambda$5007 emission, indicative of an outflow, are spatially coincident and are consistent with the interpretation of a low power radio jet interacting with the ISM. Modelling of the spectral lines using CLOUDY and MAPPINGS, and estimation of temperature using Gemini and MaNGA integral field spectroscopic data suggest shock ionization of the gas. The continuum emission at 237 GHz, though weak was found to spatially coincide with the AGN, however, the CO(2-1) line emission was found to be displaced by around 1 arcsec northward of the AGN core. The spatial coincidence of molecular H2$\lambda$2.4085 along the jet direction, the morphology of ionised [OIII]$\lambda$5007 and displacement of CO(2-1) emission argues for conditions less favourable for star formation at $\sim$5 parsec.

Abstract: Fifty years on from the first detailed chemical kinetic modelling of astronomical sources, I provide some introductory comments on the history of astrochemistry, summarise some personal views on the topics covered in this discussion meeting, and conclude with some thoughts on its future development. I have left out the jokes.

Abstract: Aims: At intermediate redshift, galaxy groups/clusters are thought to impact galaxies (e.g. their angular momentum). We investigate whether the environment has an impact on the galaxies' angular momentum and identify underlying driving physical mechanisms. Methods: We derive robust estimates of the stellar angular momentum using Hubble Space Telescope (HST) images combined with spatially resolved ionised gas kinematics from the Multi-Unit Spectroscopic Explorer (MUSE) for a sample of ~200 galaxies in groups and in the field at z~0.7 drawn from the MAGIC survey. Using various environmental tracers, we study the position of the galaxies in the the angular momentum-stellar mass (Fall) relation as a function of environment. Results: We measure a 0.12 dex (2sigma significant) depletion of angular momentum for low-mass galaxies (M* < 10^10 Msun) in groups with respect to the field. Massive galaxies located in dense environments have less angular momentum than expected from the low-mass Fall relation but, without a comparable field sample, we cannot infer whether this effect is mass- or environmentally-driven. Furthermore, massive galaxies are found in the centre of the structures and have low systemic velocities. The observed depletion of angular momentum at low mass does not appear linked with the strength of the over-density around the galaxies but it is strongly correlated with the galaxies' systemic velocity normalised by the dispersion of their host group and with their ionised gas velocity dispersion. Conclusions: Group galaxies seem depleted in angular momentum, especially at low mass. Our results suggest that this depletion might be induced by physical mechanisms that scale with the systemic velocity of the galaxies (e.g. stripping or merging) and that such mechanism might be responsible for enhancing the velocity dispersion of the gas as galaxies lose angular momentum.

Abstract: We explore the eccentricity measurement threshold of LISA for gravitational waves radiated by massive black hole binaries (MBHBs) with redshifted BH masses $M_z$ in the range $10^{4.5}\mbox{-}10^{7.5}~{\rm M}_\odot$ at redshift $z=1$. The eccentricity can be an important tracer of the environment where MBHBs evolve to reach the merger phase. To consider LISA's motion and apply the time delay interferometry, we employ the lisabeta software and produce year-long eccentric waveforms using the inspiral-only post-Newtonian model TaylorF2Ecc. We study the minimum measurable eccentricity ($e_{\rm min}$, defined at one year before the merger) analytically by computing matches and Fisher matrices, and numerically via Bayesian inference by varying both intrinsic and extrinsic parameters. We find that $e_{\rm min}$ has a strong dependence on $M_z$ and a weak dependence on mass ratio and extrinsic parameters. Match-based signal-to-noise ratio criterion suggest that LISA will be able to detect $e_{\rm min}\sim10^{-2.5}$ for lighter systems ($M_z\lesssim10^{5.5}~{\rm M}_\odot$) and $\sim10^{-1.5}$ for heavier MBHBs with a $90\%$ confidence. Bayesian inference with Fisher initialization and a zero noise realization pushes this limit to $e_{\rm min}\sim10^{-2.75}$ for lower-mass binaries assuming a $<50\%$ relative error. Bayesian inference can recover injected eccentricities of $0.1$ and $10^{-2.75}$ for a $10^5~{\rm M}_\odot$ system with a $\sim10^{-2}\%$ and a $\sim10\%$ relative errors, respectively. Both analytical and numerical methodologies provide almost consistent results for our systems of interest. LISA will launch in a decade, making this study valuable and timely to prepare for unlocking the mysteries of the MBHB evolution.

Abstract: In an earlier work, we demonstrated the effectiveness of Bayesian neural networks in estimating the missing line-of-sight velocities of Gaia stars, and published an accompanying catalogue of blind predictions for the line-of-sight velocities of stars in Gaia DR3. These were not merely point predictions, but probability distributions reflecting our state of knowledge about each star. Here, we verify that these predictions were highly accurate: the DR3 measurements were statistically consistent with our prediction distributions, with an approximate error rate of 1.5%. We use this same technique to produce a publicly available catalogue of predictive probability distributions for the 185 million stars up to a G-band magnitude of 17.5 still missing line-of-sight velocities in Gaia DR3. Validation tests demonstrate that the predictions are reliable for stars within approximately 7 kpc from the Sun and with distance precisions better than around 20%. For such stars, the typical prediction uncertainty is 25-30 km/s. We invite the community to use these radial velocities in analyses of stellar kinematics and dynamics, and give an example of such an application.

Abstract: Gravity is the driving force of star formation. Although gravity is caused by the presence of matter, its role in complex regions is still unsettled. One effective way to study the pattern of gravity is to compute the accretion it exerts on the gas by providing gravitational acceleration maps. A practical way to study acceleration is by computing it using 2D surface density maps, yet whether these maps are accurate remains uncertain. Using numerical simulations, we confirm that the accuracy of the acceleration maps $\mathbf a_{\rm 2D}(x,y)$ computed from 2D surface density are good representations for the mean acceleration weighted by mass. Due to the under-estimations of the distances from projected maps, the magnitudes of accelerations will be over-estimated $|\mathbf a_{\rm 2D}(x,y)| \approx 2.3 \pm 1.8 \; |\mathbf a_{\rm 3D}^{\rm proj}(x,y)|$, where $\mathbf a_{\rm 3D}^{\rm proj}(x,y)$ is mass-weighted projected gravitational acceleration, yet $\mathbf a_{\rm 2D}(x,y)$ and $ \mathbf a_{\rm 3D}^{\rm proj}(x,y)$ stay aligned within 20$^{\circ}$. Significant deviations only occur in regions where multiple structures are present along the line of sight. The acceleration maps estimated from surface density provide good descriptions of the projection of 3D acceleration fields. We expect this technique useful in establishing the link between cloud morphology and star formation, and in understanding the link between gravity and other processes such as the magnetic field. A version of the code for calculating surface density gravitational potential is available at \url{https://github.com/zhenzhen-research/phi_2d}.

Abstract: The broadband spectral energy distribution of a galaxy encodes valuable information on its stellar mass, star formation rate (SFR), dust content, and possible fractional energy contribution from nonstellar sources. We present a comprehensive catalog of panchromatic photometry, covering 17 bands from the far-ultraviolet to 500 $\mu$m, for 2685 low-redshift (z=0.01-0.11), massive ($M_* > 10^{10}\,M_\odot$) galaxies selected from the Stripe 82 region of the Sloan Digital Sky Survey, one of the largest areas with relatively deep, uniform observations over a wide range of wavelengths. Taking advantage of the deep optical coadded images, we develop a hybrid approach for matched-aperture photometry of the multi-band data. We derive robust uncertainties and upper limits for undetected galaxies, deblend interacting/merging galaxies and sources in crowded regions, and treat contamination by foreground stars. We perform spectral energy distribution fitting to derive the stellar mass, SFR, and dust mass, critically assessing the influence of flux upper limits for undetected photometric bands and applying corrections for systematic uncertainties based on extensive mock tests. Comparison of our measurements with those of commonly used published catalogs reveals good agreement for the stellar masses. While the SFRs of galaxies on the star-forming main sequence show reasonable consistency, galaxies in and below the green valley show considerable disagreement between different sets of measurements. Our analysis suggests that one should incorporate the most accurate and inclusive photometry into the spectral energy distribution analysis, and that care should be exercised in interpreting the SFRs of galaxies with moderate to weak star formation activity.

Abstract: Interactions and mergers play an important role in regulating the physical properties of galaxies, such as their morphology, gas content, and star formation rate (SFR). Controversy exists as to the degree to which these events, even gas-rich major mergers, enhance star formation activity. We study merger pairs selected from a sample of massive ($M_* \ge 10^{10}\,M_\odot$), low-redshift ($z = 0.01-0.11$) galaxies located in the Stripe 82 region of the Sloan Digital Sky Survey, using stellar masses, SFRs, and total dust masses derived from a new set of uniformly measured panchromatic photometry and spectral energy distribution analysis. The dust masses, when converted to equivalent total atomic and molecular hydrogen, probe gas masses as low as $\sim 10^{8.5}\,M_\odot$. Our measurements delineate a bimodal distribution on the $M_{\rm gas}-M_*$ plane: the gas-rich, star-forming galaxies that trace the well-studied gas mass main sequence, and passive galaxies that occupy a distinct, gas-poor regime. These two populations, in turn, map into a bimodal distribution on the relation between SFR and gas mass surface density. Among low-redshift galaxies, galaxy mergers, including those that involve gas-rich and nearly equal-mass galaxies, exert a minimal impact on their SFR, specific SFR, or star formation efficiency. Starbursts are rare. The star formation efficiency of gas-rich, minor mergers even appears suppressed. This study stresses the multiple, complex factors that influence the evolution of the gas and its ability to form stars in mergers.

Abstract: The origin of the radio emission in radio-quiet quasars (RQQ) is not established yet. We present new VLBA observations at 1.6 and 4.9 GHz of ten RQQ (nine detected), which together with published earlier observations of eight RQQ (five detected), forms a representative sample of 18 RQQ drawn from the Palomar-Green sample of low z (< 0.5) AGN. The spectral slope of the integrated emission extends from very steep (alpha < -1.98) to strongly inverted (alpha = +2.18), and the slopes of nine of the 14 objects are flat (alpha > -0.5). Most objects have an unresolved flat-spectrum core, which coincides with the optical Gaia position. The extended emission is generally steep-spectrum, has a low brightness temperature (< 10^7 K), and is displaced from the optical core (the Gaia position) by ~ 5-100 pc. The VLBA core flux is tightly correlated with the X-ray flux, and follows a radio to X-ray luminosity relation of log L_R/L_X = -6, for all objects with a black hole mass log M_BH/M_Sun < 8.5. The flatness of the core emission implies a compact source size (< 0.1 pc), which likely originates from the accretion disk corona. The mas-scale extended emission is optically thin and of clumpy structure, and is likely produced by an outflow from the center. Radio observations at higher frequencies can further test the accretion disk coronal emission interpretation for the core emission in RQQ.

Abstract: We present a kinematic study of a thousand of dwarf satellites of MW/M31-like hosts from the IllustrisTNG50 simulation. Internal kinematics were derived for all the snapshots to obtain a historical record of their rotation velocity in the plane of the sky ($|V_T|$) and the amplitude of their velocity gradients along the line of sight ($A_{\rm grad}^{v_z}$) measured from the host. For the majority of the satellites we initially detected rotation in the plane of the sky (65%) or velocity gradients (80%), and this was progressively reduced to 45% and 68% at $z = 0$ respectively. We find that the evolution of the rotation in the plane of the sky and the velocity gradients differs according to type of dwarfs, which could be explained in terms of their different masses and orbital histories. We observe that interaction with the host has an impact on the evolution of the internal kinematics of the satellites. The rotation signal of the satellites is progressively reduced during pericentric passages, the first pericentre being especially disruptive for the initial kinematics. We observe temporary increases in $A_{\rm grad}^{v_z}$ during pericentric passage caused by tidal interaction with the host, $A_{\rm grad}^{v_z}$ increasing as the satellites approach their pericentre and dropping as they move away. In summary, we conclude that the presence of detectable rotation in dwarf satellites is not uncommon, and that the evolution of their internal kinematics is clearly affected by their interaction with the host.