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Register a new userThe (black hole mass)-(color) relations for early- and late-type galaxies: red and blue sequences
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[Abridged] Tight correlations between supermassive black hole (SMBH) mass ($M_{rm BH}$) and the properties of the host galaxy have useful implications for our understanding of the growth of SMBHs and evolution of galaxies. Here, we present newly observed correlations between $M_{rm BH}$ and the host galaxy total UV$-$ [3.6] color ($mathcal{C_{rm UV,tot}}$, Pearsons r = $0.6-0.7$) for a sample of 67 galaxies (20 early-type galaxies and 47 late-type galaxies) with directly measured $M_{rm BH}$ in the GALEX/S$^{4}$G survey. The colors are carefully measured in a homogeneous manner using the galaxies FUV, NUV and 3.6 $micron$ magnitudes and their multi-component structural decompositions in the literature. We find that more massive SMBHs are hosted by (early- and late-type) galaxies with redder colors, but the $M_{rm BH}- mathcal{C_{rm UV,tot}}$ relations for the two morphological types have slopes that differ at $sim 2 sigma$ level. Early-type galaxies define a red sequence in the $M_{rm BH}- mathcal{C_{rm UV,tot}}$ diagrams, while late-type galaxies trace a blue sequence. Within the assumption that the specific star formation rate of a galaxy (sSFR) is well traced by $L_{rm UV}/L_{rm 3.6}$, it follows that the SMBH masses for late-type galaxies exhibit a steeper dependence on sSFR than those for early-type galaxies. The $M_{rm BH}- mathcal{C_{rm UV,tot}}$ and $M_{rm BH}-L_{rm 3.6,tot}$ relations for the sample galaxies reveal a comparable level of vertical scatter in the log $M_{rm BH}$ direction, roughly $5%-27%$ more than the vertical scatter of the $M_{rm BH}-sigma$ relation. Our $M_{rm BH}- mathcal{C_{rm UV,tot}}$ relations suggest different channels of SMBH growth for early- and late-type galaxies, consistent with their distinct formation and evolution scenarios.
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Several dedicated surveys focusing on early-type galaxies (ETGs) reveal that significant fractions of them are detectable in all interstellar medium phases studied to date. We select ETGs from the Herschel Reference Survey that have both far-infrared Herschel and either HI or CO detection (or both). We derive their star formation rates (SFR), stellar masses and dust masses via modelling their spectral energy distributions. We combine these with literature information on their atomic and molecular gas properties, in order to relate their star formation, total gas mass and dust mass on global scales. The ETGs deviate from the dust mass-SFR relation and the Schmidt-Kennicutt relation that SDSS star forming galaxies define: compared to SDSS galaxies, ETGs have more dust at the same SFR, or less SFR at the same dust mass. When placing them in the M*-SFR plane, ETGs show a much lower specific SFR as compared to normal star-forming galaxies. ETGs show a large scatter compared to the Schmidt-Kennicutt relation found locally within our Galaxy, extending to lower SFRs and gas mass surface densities. Using an ETGs SFR and the Schmidt-Kennicutt law to predict its gas mass leads to an underestimate. ETGs have similar observed-gas-to-modelled-dust mass ratios to star forming-galaxies of the same stellar mass, as well as they exhibit a similar scatter.
I review our understanding of classic dynamical scaling relations, relating luminosity, size and kinematics of early-type galaxies. Using unbiased determinations of galaxy mass profiles from stellar dynamical models, a simple picture has emerged in which scaling relations are driven by virial equilibrium, accompanied by a trend in the stellar mass-to-light ratio (M/L). This picture confirms the earliest insights. The trend is mainly due to the combined variation of age, metallicity and the stellar initial mass function (IMF). The systematic variations best correlate with the galaxy velocity dispersion, which traces the bulge mass fraction. This indicates a link between bulge growth and quenching of star formation. Dark matter is unimportant within the half-light radius, where the total mass profile is close to isothermal ($rhopropto r^{-2}$).
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.
Surface brightness-color relations (SBCRs) are used for estimating angular diameters and deriving stellar properties. They are critical to derive extragalactic distances of early-type and late-type eclipsing binaries or, potentially, for extracting planetary parameters of late-type stars hosting planets. Various SBCRs have been implemented so far, but strong discrepancies in terms of precision and accuracy still exist in the literature. We aim to develop a precise SBCR for early-type B and A stars using selection criteria, based on stellar characteristics, and combined with homogeneous interferometric angular diameter measurements. We also improve SBCRs for late-type stars, in particular in the Gaia photometric band. We observed 18 early-type stars with the VEGA interferometric instrument, installed on the CHARA array. We then applied additional criteria on the photometric measurements, together with stellar characteristics diagnostics in order to build the SBCRs. We calibrated a SBCR for subgiant and dwarf early-type stars. The RMS of the relation is $sigma_{F_{V_{0}}} = 0.0051,$mag, leading to an average precision of 2.3% on the estimation of angular diameters, with 3.1% for $V-K < -0.2,$mag and 1.8% for $V-K > -0.2,$mag. We found that the conversion between Johnson-$K$ and 2MASS-$K_s$ photometries is a key issue for early-type stars. Following this result, we have revisited our previous SBCRs for late-type stars by calibrating them with either converted Johnson-$K$ or 2MASS-$K_s$ photometries. We also improve the calibration of these SBCRs based on the Gaia photometry. The expected precision on the angular diameter using our SBCRs for late-type stars ranges from 1.0% to 2.7%. By reaching a precision of 2.3% on the estimation of angular diameters for early-type stars, significant progress has been made to determine extragalactic distances using early-type eclipsing binaries.
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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