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Register a new userDust scaling relations in a cosmological simulation
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To study the dust evolution in the cosmological structure formation history, we perform a smoothed particle hydrodynamic simulation with a dust enrichment model in a cosmological volume. We adopt the dust evolution model that represents the grain size distribution by two sizes and takes into account stellar dust production and interstellar dust processing. We examine the dust mass function and the scaling properties of dust in terms of the characteristics of galaxies. The simulation broadly reproduces the observed dust mass functions at redshift $z = 0$, except that it overproduces the massive end at dust mass $M_mathrm{d} gtrsim 10^{8}$ ${rm M}_odot$. This overabundance is due to overproducing massive gas/metal-rich systems, but we also note that the relation between stellar mass and gas-phase metallicity is reproduced fairly well by our recipe. The relation between dust-to-gas ratio and metallicity shows a good agreement with the observed one at $z=0$, which indicates successful implementation of dust evolution in our cosmological simulation. Star formation consumes not only gas but also dust, causing a decreasing trend of the dust-to-stellar mass ratio at the high-mass end of galaxies. We also examine the redshift evolution up to $z sim~ 5$, and find that the galaxies have on average the highest dust mass at $z = 1-2$. For the grain size distribution, we find that galaxies with metallicity $sim 0.3~ Z_odot$ tend to have the highest small-to-large grain abundance ratio; consequently, the extinction curves in those galaxies have the steepest ultraviolet slopes.
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The evolution of the metal content of galaxies and its relations to other global properties [such as total stellar mass (M*), circular velocity, star formation rate (SFR), halo mass, etc.] provides important constraints on models of galaxy formation. Here we examine the evolution of metallicity scaling relations of simulated galaxies in the Galaxies-Intergalactic Medium Interaction Calculation suite of cosmological simulations. We make comparisons to observations of the correlation of gas-phase abundances with M* (the mass-metallicity relation, MZR), as well as with both M* and SFR or gas mass fraction (the so-called 3D fundamental metallicity relations, FMRs). The simulated galaxies follow the observed local MZR and FMRs over an order of magnitude in M*, but overpredict the metallicity of massive galaxies (log M* > 10.5), plausibly due to inefficient feedback in this regime. We discuss the origin of the MZR and FMRs in the context of galactic outflows and gas accretion. We examine the evolution of mass-metallicity relations defined using different elements that probe the three enrichment channels (SNII, SNIa, and AGB stars). Relations based on elements produced mainly by SNII evolve weakly, whereas those based on elements produced preferentially in SNIa/AGB exhibit stronger evolution, due to the longer timescales associated with these channels. Finally, we compare the relations of central and satellite galaxies, finding systematically higher metallicities for satellites, as observed. We show this is due to the removal of the metal poor gas reservoir that normally surrounds galaxies and acts to dilute their gas-phase metallicity (via cooling/accretion onto the disk), but is lost due to ram pressure stripping for satellites.
The imprints of dust-starlight interactions are visible in scaling relations between stellar characteristics, star formation parameters and dust properties. We aim to examine dust scaling relations on a sub-kpc resolution in the Andromeda galaxy (M31) by comparing the properties on a local and global scale to other galaxies of the local universe. New Herschel observations are combined with available data from GALEX, SDSS, WISE and Spitzer to construct a dataset covering UV to submm wavelengths. We work at the resolution of the SPIRE $500; mu$m beam, with pixels corresponding to physical regions of 137 x 608 pc in the galaxys disk. A panchromatic spectral energy distribution was modelled for each pixel and several dust scaling relations are investigated. We find, on a sub-kpc scale, strong correlations between $M_d/M_star$ and NUV-r, and between $M_d/M_star$ and $mu_star$ (the stellar mass surface density). Striking similarities with corresponding relations based on integrated galaxies are found. We decompose M31 in four macro-regions based on their FIR morphology; the bulge, inner disk, star forming ring and the outer disk. All regions closely follow the galaxy-scale average trends. The specific star formation characteristics we derive for these macro-regions give strong hints of an inside-out formation of the bulge-disk geometry, as well as an internal downsizing process. However, within each macro-region, a great diversity in individual micro-regions is found. Furthermore, we confirm that dust in the bulge of M31 is heated only by the old stellar populations. In general, the local dust scaling relations indicate that the dust content in M31 is maintained by a subtle interplay of past and present star formation. The similarity with galaxy-based relations strongly suggests that they are in situ correlations, with underlying processes that must be local in nature. (Abriged)
Observations of interstellar dust are often used as a proxy for total gas column density $N_mathrm{H}$. By comparing $textit{Planck}$ thermal dust data (Release 1.2) and new dust reddening maps from Pan-STARRS 1 and 2MASS (Green et al. 2018), with accurate (opacity-corrected) HI column densities and newly-published OH data from the Arecibo Millennium survey and 21-SPONGE, we confirm linear correlations between dust optical depth $tau_{353}$, reddening $E(B{-}V)$ and the total proton column density $N_mathrm{H}$ in the range (1$-$30)$times$10$^{20}$cm$^{-2}$, along sightlines with no molecular gas detections in emission. We derive an $N_mathrm{H}$/$E(B{-}V)$ ratio of (9.4$pm$1.6)$times$10$^{21}$cm$^{-2}$mag$^{-1}$ for purely atomic sightlines at $|b|$$>$5$^{circ}$, which is 60$%$ higher than the canonical value of Bohlin et al. (1978). We report a $sim$40$%$ increase in opacity $sigma_{353}$=$tau_{353}$/$N_mathrm{H}$, when moving from the low column density ($N_mathrm{H}$$<$5$times$10$^{20}$cm$^{-2}$) to moderate column density ($N_mathrm{H}$$>$5$times$10$^{20}$cm$^{-2}$) regime, and suggest that this rise is due to the evolution of dust grains in the atomic ISM. Failure to account for HI opacity can cause an additional apparent rise in $sigma_{353}$, of the order of a further $sim$20$%$. We estimate molecular hydrogen column densities $N_{mathrm{H}_{2}}$ from our derived linear relations, and hence derive the OH/H$_2$ abundance ratio of $X_mathrm{OH}$$sim$1$times$10$^{-7}$ for all molecular sightlines. Our results show no evidence of systematic trends in OH abundance with $N_{mathrm{H}_{2}}$ in the range $N_{mathrm{H}_{2}}$$sim$(0.1$-$10)$times$10$^{21}$cm$^{-2}$. This suggests that OH may be used as a reliable proxy for H$_2$ in this range, which includes sightlines with both CO-dark and CO-bright gas.
X-ray luminosity, temperature, gas mass, total mass, and their scaling relations are derived for 94 early-type galaxies using archival $Chandra$ X-ray Observatory observations. Consistent with earlier studies, the scaling relations, $L_X propto T^{4.5pm0.2}$, $M propto T^{2.4pm0.2}$, and $L_X propto M^{2.8pm0.3}$, are significantly steeper than expected from self similarity. This steepening indicates that their atmospheres are heated above the level expected from gravitational infall alone. Energetic feedback from nuclear black holes and supernova explosions are likely heating agents. The tight $L_X - T$ correlation for low-luminosities systems (i.e., below 10$^{40}$ erg/s) are at variance with hydrodynamical simulations which generally predict higher temperatures for low luminosity galaxies. We also investigate the relationship between total mass and pressure, $Y_X = M_g times T$, finding $M propto Y_{X}^{0.45pm0.04}$. We explore the gas mass to total mass fraction in early-type galaxies and find a range of $0.1-1.0%$. We find no correlation between the gas-to-total mass fraction with temperature or total mass. Higher stellar velocity dispersions and higher metallicities are found in hotter, brighter, and more massive atmospheres. X-ray core radii derived from $beta$-model fitting are used to characterize the degree of core and cuspiness of hot atmospheres.
We investigate the black hole (BH) scaling relation in galaxies using a model in which the galaxy halo and central BH are a self-gravitating sphere of dark matter (DM) with an isotropic, adiabatic equation of state. The equipotential where the escape velocity approaches the speed of light defines the horizon of the BH. We find that the BH mass ($m_bullet$) depends on the DM entropy, when the effective thermal degrees of freedom ($F$) are specified. Relations between BH and galaxy properties arise naturally, with the BH mass and DM velocity dispersion following $m_bulletproptosigma^{F/2}$ (for global mean density set by external cosmogony). Imposing observationally derived constraints on $F$ provides insight into the microphysics of DM. Given that DM velocities and stellar velocities are comparable, the empirical correlation between $m_bullet$ and stellar velocity dispersions $sigma_star$ implies that $7<F<10$. A link between $m_bullet$ and globular cluster properties also arises because the halo potential binds the globular cluster swarm at large radii. Interestingly, for $F>6$ the dense dark envelope surrounding the BH approaches the mean density of the BH itself, while the outer halo can show a nearly uniform kpc-scale core resembling those observed in galaxies.
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