N. Nowak

Spectroscopy of clusters in the ESO distant cluster survey (EDisCS) - II. Redshifts, velocity dispersions, and substructure for clusters in the last 15 fields

Aims. We present spectroscopic observations of galaxies in 15 survey fields as part of the ESO Distant Cluster Survey (EDisCS). We determine the redshifts and velocity dispersions of the galaxy clusters located in these fields, and we test for possible substructure in the clusters. Methods: We obtained multi-object mask spectroscopy using the FORS2 instrument at the VLT. We reduced the data with particular attention to the sky subtraction. We implemented the method of Kelson for performing sky subtraction prior to any rebinning/interpolation of the data. From the measured galaxy redshifts, we determine cluster velocity dispersions using the biweight estimator and test for possible substructure in the clusters using the Dressler-Shectman test. Results: The method of subtracting the sky prior to any rebinning/interpolation of the data delivers photon-noise-limited results, whereas the traditional method of subtracting the sky after the data have been rebinned/interpolated results in substantially larger noise for spectra from tilted slits. Redshifts for individual galaxies are presented and redshifts and velocity dispersions are presented for 21 galaxy clusters. For the 9 clusters with at least 20 spectroscopically confirmed members, we present the statistical significance of the presence of substructure obtained from the Dressler-Shectman test, and substructure is detected in two of the clusters. Conclusions: Together with data from our previous paper, spectroscopy and spectroscopic velocity dispersions are now available for 26 EDisCS clusters with redshifts in the range 0.40-0.96 and velocity dispersions in the range 166 km s-1-1080 km s-1. Based on observations collected at the European Southern Observatory, Chile, as part of large programme 166.A-0162 (the ESO Distant Cluster Survey). Full Table 4 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/482/419

Do black hole masses scale with classical bulge luminosities only? The case of the two composite pseudo-bulge galaxies NGC 3368 and NGC 3489

It is now well established that all galaxies with a massive bulge component harbour a central supermassive black hole (SMBH). The mass of the SMBH correlates with bulge properties such as the bulge mass and the velocity dispersion, which implies that the bulge and the central black hole of a galaxy have grown together during the formation process. As part of an investigation of the dependence of the SMBH mass on bulge types and formation mechanisms, we present measurements of SMBH masses in two pseudobulge galaxies. The spiral galaxy NGC 3368 is double-barred and hosts a large pseudobulge with a tiny classical bulge component at the very centre. The S0 galaxy NGC 3489 has only a weak large-scale bar, a small pseudobulge and a small classical bulge. Both galaxies show weak nuclear activity in the optical, indicative of the presence of a supermassive black hole. We present high resolution, adaptive-optics-assisted, near-infrared integral field data of these two galaxies, taken with SINFONI at the Very Large Telescope, and use axisymmetric orbit models to determine the masses of the SMBHs. The SMBH mass of NGC 3368, averaged over the four quadrants, ishM i = 7:5 10 6 M with an error of 1:5 10 6 M , which mostly comes from the non-axisymmetry in the data. For NGC 3489, a solution without black hole cannot be excluded when modelling the SINFONI data alone, but can be clearly ruled out when modelling a combination of SINFONI, OASIS and SAURON data, for which we obtain M = (6:00 +0:56 0:54 jstat 0:64jsys) 10 6 M . Although both galaxies seem to be consistent with the M - relation, at face value they do not agree with the relation between bulge magnitude and black hole mass when the total bulge magnitude (i.e., including both classical bulge and pseudobulge) is considered; the agreement is better when only the small classical bulge components are considered. However, taking into account the ageing of the stellar population could change this conclusion.

The central black hole mass of the high-σ but low-bulge-luminosity lenticular galaxy NGC 1332

The masses of the most massive supermassive black holes (SMBHs) predicted by the M BH -σ and M BH -L relations appear to be in conflict. Which of the two relations is the more fundamental one remains an open question. NGC 1332 is an excellent example that represents the regime of conflict. It is a massive lenticular galaxy which has a bulge with a high velocity dispersion σ of ~320 km s -1 ; bulge-disc decomposition suggests that only 44 per cent of the total light comes from the bulge. The M BH -σ and the M BH -L predictions for the central black hole mass of NGC 1332 differ by almost an order of magnitude. We present a stellar dynamical measurement of the SMBH mass using an axisymmetric orbit superposition method. Our SINFONI integral-field unit (IFU) observations of NGC 1332 resolve the SMBHs sphere of influence which has a diameter of ~0.76 arcsec. The σ inside 0.2 arcsec reaches ~400 km s -1 . The IFU data allow us to increase the statistical significance of our results by modelling each of the four quadrants separately. We measure an SMBH mass of (1.45 ± 0.20) x 10 9 M ⊙ with a bulge mass-to-light ratio of 7.08 ± 0.39 in the R band. With this mass, the SMBH of NGC 1332 is offset from the M BH -L relation by a full order of magnitude but is consistent with the M BH -σ relation.

The supermassive black hole of Fornax A

The radio galaxy Fornax A (NGC 1316) is a prominent merger remnant in the outskirts of the Fornax cluster. Its giant radio lobes suggest the presence of a powerful active galactic nuclei (AGN) and thus a central supermassive black hole (SMBH). FomaxA now seems to be in a transition state between active black hole growth and quiescence, as indicated by the strongly declined activity of the nucleus. Studying objects in this evolutionary phase is particularly important in order to understand the link between bulge formation and black hole growth, which is manifested in the M • -σ relation between black hole mass and bulge velocity dispersion. So far, a measurement of the SMBH mass has not been possible in Fomax A, as it is enshrouded in dust which makes optical measurements impossible. We present high-resolution adaptive optics assisted integral-field data of Fomax A, taken with SINFONI at the Very Large Telescope in the K band, where the influence of dust is negligible. The achieved spatial resolution is 0.085 arcsec, which is about a fifth of the diameter of the expected sphere of influence of the black hole. The stellar kinematics was measured using the region around the CO bandheads at 2.3 μm. Fornax A does not rotate inside the inner ∼3 arcsec. The velocity dispersion increases towards the centre. The weak AGN emission affects the stellar kinematics in the inner ∼0.06 arcsec only. Beyond this radius, the stellar kinematics appears relaxed in the central regions. We use axisymmetric orbit models to determine the mass of the SMBH in the centre of Fornax A. The three-dimensional nature of our data provides the possibility to directly test the consistency of the data with axisymmetry by modelling each of the four quadrants separately. According to our dynamical models, consistent SMBH masses M • and dynamical K s -band mass-to-light ratios T are obtained for all quadrants, with (M • ) = 1.3 x 10 8 M ⊙ [rms(M.) = 0.4 x 10 8 M ⊙ ] and (T) = 0.68 [rms(T) = 0.03], confirming the assumption of axisymmetry. For the folded and averaged data, we find M. = 1.5 +0.75 -0.8 x 10 8 M ⊙ and T = 0.65 +0.075 -0.05 (3σ errors). Thus, the black hole mass of Fomax A is consistent within the error with the Tremaine et al. M • -σ relation, but is a factor of ∼4 smaller than expected from its bulge mass and the Marconi & Hunt relation.

The supermassive black hole in NGC 4486a detected with SINFONI at the very large telescope

The near-infrared (IR) integral field spectrograph SINFONI at the European Southern Observatory Very Large Telescope opens a new window for the study of central supermassive black holes. With a near-IR spatial resolution similar to Hubble Space Telescope optical and the ability to penetrate dust, it provides the possibility to explore the low-mass end of the M•‐σ relation ( σ< 120 km s −1 ) where so far very few black hole masses were measured with stellar dynamics. With SINFONI, we observed the central region of the low-luminosity elliptical galaxy NGC 4486a at a spatial resolution of ≈0.1 arcsec in the K band. The stellar kinematics were measured with a maximum penalized likelihood method considering the region around the CO absorption band heads. We determined a black hole mass of M• = (1.25 +0.75 −0.79) × 10 7 M� (90 per cent confidence limit) using the Schwarzschild orbit superposition method including the full two-dimensional spatial information. This mass agrees with the predictions of the M•‐σ relation, strengthening its validity at the lower σ end.

Molecular gas in the centre of nearby galaxies from VLT/SINFONI integral field spectroscopy – I. Morphology and mass inventory

We present the first results of an analysis of the properties o f 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, Brγ 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 H 2 2.12µm emission-line luminosity by a factorβ≃ 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 ∼ 10 5 − 10 8 M⊙ 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 Brγ equivalent width and the Hei/Brγ emission-line ratio suggests that bursts of star formation occurred throughout this ring as recently as 6.5 Myr ago.

THE SINFONI BLACK HOLE SURVEY: THE BLACK HOLE FUNDAMENTAL PLANE REVISITED AND THE PATHS OF (CO)EVOLUTION OF SUPERMASSIVE BLACK HOLES AND BULGES

We investigate the correlations between the black hole mass

The extended ROSAT-ESO Flux-Limited X-ray Galaxy Cluster Survey (REFLEX II) – III. Construction of the first flux-limited supercluster sample

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The extended ROSAT-ESO flux limited X-ray galaxy cluster survey (REFLEX II) - II. Construction and properties of the survey

, the velocity dispersion

Molecular gas in the centre of nearby galaxies from VLT/SINFONI integral field spectroscopy – II. Kinematics

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