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 / L V ≈ 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 / L V (≈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.

The Andromeda galaxy (M31) contains a box/peanut bulge (BPB) entangled with a classical bulge (CB) requiring a triaxial modelling to determine the dynamics, stellar, and dark matter mass. We construct made-to-measure models fitting new VIRUS-W IFU bulge stellar kinematic observations, the IRAC-3.6 mu m photometry, and the disc's HI rotation curve. We explore the parameter space for the 3.6 mu m mass-to-light ratio ((sic)(3.6)), the bar pattern speed (Omega(p)), and the dark matter mass in the composite bulge (M-DM(B)) within 3.2 kpc. Considering Einasto dark matter profiles, we find the best models for (sic)(3.6) = 0.72 +/- 0.02 M circle dot L circle dot-1, M-DM(B) = 1.2(-0.4)(+0.2) x 10(10) M-circle dot, and Omega(p) = 40 +/- 5 km s(-1) kpc(-1). These models have a dynamical bulge mass of M-dyn(B) = 4.25(-0.29)(+0.10) x 10(10) M-circle dot including a stellar mass of M-star(B) = 3.09(-0.12)(+ 0.10) x 10(10) M-circle dot (73 per cent), of which the CB has M-star(CB) = 1.18(-0.07)(+0.06)x 10(10) M-circle dot (28 per cent) and the BPB M-star(BPB) = 1.91 +/- 0.06 x 10(10) M-circle dot (45 per cent). We also explore models with NFW haloes finding that, while the Einasto models better fit the stellar kinematics, the obtained parameters agree within the errors. The M-DM(B) values agree with adiabatically contracted cosmological NFW haloes with M31's virial mass and radius. The best model has two bulge components with completely different kinematics that only together successfully reproduce the observations (mu(3.6), upsilon(los), sigma(los), h3, h4). The modelling includes dust absorption which reproduces the observed kinematic asymmetries. Our results provide new constraints for the early formation of M31 given the lower mass found for the classical bulge and the shallow dark matter profile, as well as the secular evolution of M31 implied by the bar and its resonant interactions with the classical bulge, stellar halo and disc.

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.

Andromeda is our nearest neighbouring disc galaxy and a prime target for detailed modelling of the evolutionary processes that shape galaxies. We analyse the nature of M31's triaxial bulge with an extensive set ofN-body models, which include box/peanut (B/P) bulges as well as initial classical bulges (ICBs). Comparing with Infrared Array Camera (IRAC) 3.6 mu m data, only one model matches simultaneously all the morphological properties of M31's bulge, and requires an ICB and a B/P bulge with 1/3 and 2/3 of the total bulge mass, respectively. We find that our pure B/P bulge models do not show concentrations high enough to match the Sersic index (n) and the effective radius of M31's bulge. Instead, the best model requires an ICB component with mass M-ICB = 1.1 x 10(10)M(circle dot) and 3D half-mass radius r(half)(ICB) = 0.53 kpc (140 arcsec). The B/P bulge component has a mass of M-B/P = 2.2 x 10(10)M(circle dot) and a half-mass radius of r(half)(B/P) = 1.3 kpc (340 arcsec). The model's B/P bulge extends to r(B/P) = 3.2 kpc (840 arcsec) in the plane of the disc as does M31's bulge. In this composite bulge model, the ICB component explains the velocity dispersion drop observed in the centre within R < 190 pc (50 arcsec), while the B/P bulge component reproduces the observed rapid rotation and the kinematic twist of the observed zero velocity line. This model's pattern speed is Omega(p) = 38 km s(-1) kpc(-1), placing corotation at r(cor) = 5.8 kpc (1500 arcsec). The outer Lindblad resonance (OLR) is then at r(OLR) = 10.4 kpc, near the 10 kpc ring of M31, suggesting that this structure may be related to the bar's OLR. By comparison with an earlier snapshot, we estimate that M31's thin bar extends to r(bar)(thin) similar to 4.0 kpc (1000 arcsec) in the disc plane, and in projection extends to R-bar(thin) similar to 2.3 kpc (600 arcsec).

We investigate the correlations between the black hole (BH) 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, 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 M-BH-sigma and M-BH-M-Bu relations and establish the existence of statistically significant correlations between M-Bu and r(h) and anticorrelations 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 MBH of 77 core and power-law ellipticals and classical bulges with measured and intrinsic scatter as small as approximate to 0.36 dex and approximate to 0.33 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 rho(h) >= 10(10) M-circle dot kpc(-3). or scale lengths r(h) <= 1 kpc. 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.

AbstractWe have collected optical integral field spectroscopic data for M31 with the spectrograph VIRUS-W that result in kinematic maps of unprecedented detail. These reveal the presence of two kinematically distinct gas components.

Most Milky Way globular clusters (GCs) exhibit measurable flattening, even if on a very low level. Both cluster rotation and tidal fields are thought to cause this flattening. Nevertheless, rotation has only been confirmed in a handful of GCs, based mostly on individual radial velocities at large radii. We are conducting a survey of the central kinematics of Galactic GCs using the new Integral Field Unit instrument VIRUS-W. We detect rotation in all 11 GCs that we have observed so far, rendering it likely that a large majority of the Milky Way GCs rotate. We use published catalogs of the ACS survey of GCs to derive central ellipticities and position angles. We show that in all cases where the central ellipticity permits an accurate measurement of the position angle, those angles are in excellent agreement with the kinematic position angles that we derive from the VIRUS-W velocity fields. We find an unexpected tight correlation between central rotation and outer ellipticity, indicating that rotation drives flattening for the objects in our sample. We also find a tight correlation between central rotation and published values for the central velocity dispersion, most likely due to rotation impacting the old dispersion measurements.

We present the first results of an analysis of the properties of the molecular gas in the nuclear regions (r less than or similar to 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 H-2, Br gamma 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 H-2 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 H-2 2.12 mu m emission-line luminosity by a factor beta similar or equal to 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 similar to 10(5)-10(8)M(circle dot) 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 similar to 270 pc) in the galaxy NGC 4536. The measured values of the Br gamma equivalent width and the He I/Br gamma emission-line ratio suggest that bursts of star formation occurred throughout this ring as recently as 6.5 Myr ago.