ABSTRACT We investigate the correlations between the black hole (BH) mass MBH, the velocity dispersion , the bulge mass MBu, the bulge average spherical density , and its spherical half-mass radius ...rh, constructing a database of 97 galaxies (31 core ellipticals, 17 power-law ellipticals, 30 classical bulges, and 19 pseudobulges) by joining 72 galaxies from the literature to 25 galaxies observed during our recent SINFONI BH survey. For the first time we discuss the full error covariance matrix. We analyze the well-known MBH- and MBH-MBu relations and establish the existence of statistically significant correlations between MBu and rh and anticorrelations between MBu and . We establish five significant bivariate correlations (MBH- - h, MBH- -rh, MBH-MBu- , MBH-MBu- h, MBH-MBu-rh) that predict MBH of 77 core and power-law ellipticals and classical bulges with measured and intrinsic scatter as small as dex and dex, respectively, or 0.26 dex when the subsample of 45 galaxies defined by Kormendy & Ho is considered. In contrast, pseudobulges have systematically lower MBH but approach the predictions of all of the above relations at spherical densities or scale lengths . These findings fit in a scenario of coevolution of BH and classical-bulge masses, where core ellipticals are the product of dry mergers of power-law bulges and power-law ellipticals and bulges the result of (early) gas-rich mergers and of disk galaxies. In contrast, the (secular) growth of BHs is decoupled from the growth of their pseudobulge hosts, except when (gas) densities are high enough to trigger the feedback mechanism responsible for the existence of the correlations between MBH and galaxy structural parameters.
Aim.
As the nearest large spiral galaxy, M 31 provides a unique opportunity to study the structure and evolutionary history of this galaxy type in great detail. Among the many observing programs ...aimed at M 31 are microlensing studies, which require good three-dimensional models of the stellar mass distribution. Possible non-axisymmetric structures like a bar need to be taken into account. Due to M 31’s high inclination, the bar is difficult to detect in photometry alone. Therefore, detailed kinematic measurements are needed to constrain the possible existence and position of a bar in M 31.
Methods.
We obtained ≈220 separate fields with the optical integral-field unit spectrograph VIRUS-W, covering the whole bulge region of M 31 and parts of the disk. We derived stellar line-of-sight velocity distributions from the stellar absorption lines, as well as velocity distributions and line fluxes of the emission lines H
β
, O
III
and N
I
. Our data supersede any previous study in terms of spatial coverage and spectral resolution.
Results.
We find several features that are indicative of a bar in the kinematics of the stars, we see intermediate plateaus in the velocity and the velocity dispersion, and correlation between the higher moment
h
3 and the velocity. The gas kinematics is highly irregular, but is consistent with non-triaxial streaming motions caused by a bar. The morphology of the gas shows a spiral pattern, with seemingly lower inclination than the stellar disk. We also look at the ionization mechanisms of the gas, which happens mostly through shocks and not through starbursts.
We present the first results of an analysis of the properties of the molecular gas in the nuclear regions (r 300 pc) of a sample of six nearby galaxies, based on new high-spatial-resolution ...observations obtained in the K-band with the near-infrared integral field spectrograph SINFONI at the Very Large Telescope. We derive 2D distributions of the warm molecular and ionized gas from the H2, Brγ and He i emission lines present in the spectra of the galaxies. We find a range of morphologies, including bar- and ring-like distributions and either centrally peaked or off-centre emission. The morphologies of the molecular and the ionized gas are not necessarily coincident. The observed emission-line ratios point towards thermal processes as the principal mechanism responsible for the H2 excitation in the nuclear and circumnuclear regions of the galaxies, independently of the presence of an active nucleus. We find that a rescaling of the H2 2.12 μm emission-line luminosity by a factor β 1200 gives a good estimate (within a factor of 2) of the total (cold) molecular gas mass. The galaxies of the sample contain large quantities of molecular gas in their centres, with total masses in the ∼105-108 M range. Nevertheless, these masses correspond to less than 3 per cent of the stellar masses derived for the galaxies in these regions, indicating that the presence of gas should not affect black hole mass estimates based on the dynamical modelling of the stars. The high spatial resolution provided by the SINFONI data allowed us to resolve a circumnuclear ring (with a radius of ∼270 pc) in the galaxy NGC 4536. The measured values of the Brγ equivalent width and the He i/Brγ emission-line ratio suggest that bursts of star formation occurred throughout this ring as recently as 6.5 Myr ago.
Aims. We continue the analysis of the data set of our spectroscopic observation campaign of M 31, whose ultimate goal is to provide an understanding of the three-dimensional structure of the bulge, ...its formation history, and composition in terms of a classical bulge, boxy-peanut bulge, and bar contributions. Methods. We derive simple stellar population (SSP) properties, such as age metallicity and α-element overabundance, from the measurement of Lick/IDS absorption line indices. We describe their two-dimensional maps taking into account the dust distribution in M 31. Results. We found 80% of the values of our age measurements are larger than 10 Gyr. The central 100 arcsec of M 31 are dominated by the stars of the classical bulge of M 31. These stars are old (11−13 Gyr), metal-rich (as high as Z/H ≈ 0.35 dex) at the center with a negative gradient outward and enhanced in α-elements (α/Fe≈ 0.28±0.01 dex). The bar stands out in the metallicity map, where an almost solar value of Z/H (≈0.02 ± 0.01 dex) with no gradient is observed along the bar position angle (55.7 deg) out to 600 arcsec from the center. In contrast, no signature of the bar is seen in the age and α/Fe maps, which are approximately axisymmetric, delivering a mean age and overabundance for the bar and boxy-peanut bulge of 10–13 Gyr and 0.25–0.27 dex, respectively. The boxy-peanut bulge has almost solar metallicity (−0.04 ± 0.01 dex). The mass-to-light ratio of the three components is approximately constant at M/LV ≈ 4.4−4.7 M⊙/L⊙. The disk component at larger distances is made of a mixture of stars, as young as 3–4 Gyr, with solar metallicity and smaller M/LV (≈3 ± 0.1 M⊙/L⊙). Conclusions. We propose a two-phase formation scenario for the inner region of M 31, where most of the stars of the classical bulge come into place together with a proto-disk, where a bar develops and quickly transforms it into a boxy-peanut bulge. Star formation continues in the bulge region, producing stars younger than 10 Gyr, in particular along the bar, thereby enhancing its metallicity. The disk component appears to build up on longer timescales.
Aim. As the nearest large spiral galaxy, M 31 provides a unique opportunity to study the structure and evolutionary history of this galaxy type in great detail. Among the many observing programs ...aimed at M 31 are microlensing studies, which require good three-dimensional models of the stellar mass distribution. Possible non-axisymmetric structures like a bar need to be taken into account. Due to M 31’s high inclination, the bar is difficult to detect in photometry alone. Therefore, detailed kinematic measurements are needed to constrain the possible existence and position of a bar in M 31. Methods. We obtained ≈220 separate fields with the optical integral-field unit spectrograph VIRUS-W, covering the whole bulge region of M 31 and parts of the disk. We derived stellar line-of-sight velocity distributions from the stellar absorption lines, as well as velocity distributions and line fluxes of the emission lines Hβ, O III and N I. Our data supersede any previous study in terms of spatial coverage and spectral resolution. Results. We find several features that are indicative of a bar in the kinematics of the stars, we see intermediate plateaus in the velocity and the velocity dispersion, and correlation between the higher moment h3 and the velocity. The gas kinematics is highly irregular, but is consistent with non-triaxial streaming motions caused by a bar. The morphology of the gas shows a spiral pattern, with seemingly lower inclination than the stellar disk. We also look at the ionization mechanisms of the gas, which happens mostly through shocks and not through starbursts.
We continue the analysis of the dataset of our spectroscopic observation campaign of M31, by deriving simple stellar population properties (age metallicity and alpha-elements overabundance) from the ...measurement of Lick/IDS absorption line indices. We describe their two-dimensional maps taking into account the dust distribution in M31. 80\% of the values of our age measurements are larger than 10 Gyr. The central 100 arcsec of M31 are dominated by the stars of the classical bulge of M31. They are old (11-13 Gyr), metal-rich (as high as Z/H~0.35 dex) at the center with a negative gradient outwards and enhanced in alpha-elements (alpha/Fe~ 0.28+- 0.01 dex). The bar stands out in the metallicity map, where an almost solar value of Z/H (~0.02+-0.01 dex) with no gradient is observed along the bar position angle (55.7 deg) out to 600 arcsec from the center. In contrast, no signature of the bar is seen in the age and alpha/Fe maps, that are approximately axisymmetric, delivering a mean age and overabundance for the bar and the boxy-peanut bulge of 10-13 Gyr and 0.25-0.27 dex, respectively. The boxy/peanut-bulge has almost solar metallicity (-0.04+- 0.01 dex). The mass-to-light ratio of the three components is approximately constant at M/LV ~ 4.4-4.7 Msol/Lsol. The disk component at larger distances is made of a mixture of stars, as young as 3-4 Gyr, with solar metallicity and smaller M/LV (~3+-0.1 Msol/Lsol). We propose a two-phase formation scenario for the inner region of M31, where most of the stars of the classical bulge come into place together with a proto-disk, where a bar develops and quickly transforms it into a boxy-peanut bulge. Star formation continues in the bulge region, producing stars younger than 10 Gyr, in particular along the bar, enhancing its metallicity. The disk component appears to build up on longer time-scales.
We investigate the correlations between the black hole mass \(M_{BH}\), the velocity dispersion \(\sigma\), the bulge mass \(M_{Bu}\), the bulge average spherical density \(\rho_h\) and its spherical ...half mass radius \(r_h\), constructing a database of 97 galaxies (31 core ellipticals, 17 power-law ellipticals, 30 classical bulges, 19 pseudo bulges) by joining 72 galaxies from the literature to 25 galaxies observed during our recent SINFONI black hole survey. For the first time we discuss the full error covariance matrix. We analyse the well known \(M_{BH}-\sigma\) and \(M_{BH}-M_{Bu}\) relations and establish the existence of statistically significant correlations between \(M_{Bu}\) and \(r_h\) and anti-correlations between \(M_{Bu}\) and \(\rho_h\). We establish five significant bivariate correlations (\(M_{BH}-\sigma-\rho_h\), \(M_{BH}-\sigma-r_h\), \(M_{BH}-M_{Bu}-\sigma\), \(M_{BH}-M_{Bu}-\rho_h\), \(M_{BH}-M_{Bu}-r_h\)) that predict \(M_{BH}\) of 77 core and power-law ellipticals and classical bulges with measured and intrinsic scatter as small as \(\approx 0.36\) dex and \(\approx 0.33\) dex respectively, or 0.26 dex when the subsample of 45 galaxies defined by Kormendy and Ho (2013) is considered. In contrast, pseudo bulges have systematically lower \(M_{BH}\), but approach the predictions of all the above relations at spherical densities \(\rho_h\ge 10^{10} M_\odot/kpc^3\) or scale lengths \(r_h\le 1\) kpc. These findings fit in a scenario of co-evolution of BH and classical-bulge masses, where core ellipticals are the product of dry mergers of power-law bulges and power-law Es and bulges the result of (early) gas-rich mergers and of disk galaxies. In contrast, the (secular) growth of BHs is decoupled from the growth of their pseudo bulge hosts, except when (gas) densities are high enough to trigger the feedback mechanism responsible for the existence of the correlations between \(M_{BH}\) and galaxy structural parameters.
We present the first results of an analysis of the properties of the molecular gas in the nuclear regions (r < 300 pc) of a sample of six nearby galaxies, based on new high spatial resolution ...observations obtained in the K-band with the near-infrared integral field spectrograph SINFONI at the Very Large Telescope. We derive two-dimensional distributions of the warm molecular and ionized gas from the H2, Br_gamma and HeI emission lines present in the spectra of the galaxies. We find a range of morphologies, including bar- and ring-like distributions and either centrally peaked or off-centre emission. The morphologies of the molecular and the ionized gas are not necessarily coincident. The observed emission-line ratios point towards thermal processes as the principal mechanism responsible for the H2 excitation in the nuclear and circumnuclear regions of the galaxies, independently of the presence of an active nucleus. We find that a rescaling of the H2 2.12 microns emission-line luminosity by a factor beta~1200 gives a good estimate (within a factor of 2) of the total (cold) molecular gas mass. The galaxies of the sample contain large quantities of molecular gas in their centres, with total masses in the ~ 105 - 108 Msol range. Never the less, these masses correspond to less than 3 per cent of the stellar masses derived for the galaxies in these regions, indicating that the presence of gas should not affect black hole mass estimates based on the dynamical modelling of the stars. The high-spatial resolution provided by the SINFONI data allowed us to resolve a circumnuclear ring (with a radius of ~270 pc) in the galaxy NGC 4536. The measured values of the Br_gamma equivalent width and the HeI/Br_gamma emission-line ratio suggests that bursts of star formation occurred throughout this ring as recently as 6.5 Myr ago.
PDF
