ALBERT

Beschreibung: We present the properties of the central supermassive black holes and the host galaxies of the interacting object SDSS J134420.86+663717.8. We obtained optical long slit spectroscopy data from the Large Binocular Telescope using the Multi Object Double Spectrograph. Analysing the spectra revealed several strong broad and narrow emission lines of ionised gas in the nuclear region of one galaxy, whereas only narrow emission lines were visible for the second galaxy. The optical spectra were used to plot diagnostic diagrams, deduce rotation curves of the two galaxies, and calculate the masses of the central supermassive black holes. We find that the galaxy with broad emission line features has Seyfert 1 properties, while the galaxy with only narrow emission line features seems to be star-forming in nature. Furthermore, we find that the masses of the central supermassive black holes are almost equal at a few times 107 M⊙. Additionally, we present a simple N-body simulation to shed some light on the initial conditions of the progenitor galaxies. We find that for an almost orthogonal approach of the two interacting galaxies, the model resembles the optical image of the system.

Beschreibung: Context. The empirical relations between supermassive black holes and their host spheroids point towards the crucial role of galactic nuclei in affecting the properties of their hosts. A detailed understanding of how the activity of a galactic nucleus regulates the growth of its host is still missing. Aims. To understand the activity and the types of accretion of supermassive black holes in different hosts, it is essential to study the radio-optical properties of a large sample of extragalactic sources. In particular, we aim to study the radio spectral index trends across the optical emission line diagnostic diagrams to search for potential (anti)correlations. Methods. To this goal, we combined flux densities from the radio FIRST survey at 1.4 GHz (with the flux density range 10 mJy ≤ F1.4 ≤ 100 mJy) for 396 SDSS sources at intermediate redshift (0.04 ≤ z ≤ 0.4) with the Effelsberg radiotelescope measurements at 4.85 GHz and 10.45 GHz. The information about the optical emission-line ratios is obtained from the SDSS-DR7 catalogue. Results. Using the Effelsberg data, we were able to infer the two-point radio spectral index distributions for star-forming galaxies, composite galaxies (with a combined contribution to the line emission from the star formation and AGN activity), Seyferts, and low ionization narrow emission region (LINER) galaxies. Conclusions. While studying the distribution of steep, flat, and inverted sources across optical diagnostic diagrams, we found three distinct classes of radio emitters for our sample: (i) sources with a steep radio index, high ionization ratio, and high radio loudness, (ii) sources with a flat radio index, lower ionization ratio, and intermediate radio loudness, (iii) sources with an inverted radio index, low ionization ratio, and low radio loudness. The classes (i), (ii), and (iii) cluster mainly along the transition from Seyfert to LINER sources in the optical diagnostic (Baldwin, Phillips & Telervich; BPT) diagram. We interpret these groups as a result of the recurrent nuclear-jet activity.

Beschreibung: In the framework of understanding the gas and stellar kinematics and their relations to AGNs and galaxy evolution scenarios, we present spatially resolved distributions and kinematics of the stars and gas in the central ∼800 pc radius of the nearby Seyfert galaxy NGC 1365. We obtained H + K- and K-band near-infrared (NIR) integral-field observations from VLT/SINFONI. Our results reveal strong broad and narrow emission-line components of ionized gas (hydrogen recombination lines Paα and Brγ) in the nuclear region, as well as hot dust with a temperature of ∼1300 K, both typical for type-1 AGNs. From MBH − σ* and the broad components of hydrogen recombination lines, we find a black-hole mass of (5 − 10)×106 M⊙. In the central ∼800 pc, we find a hot molecular gas mass of ∼615 M⊙, which corresponds to a cold molecular gas reservoir of (2 − 8)×108 M⊙. However, there is a molecular gas deficiency in the nuclear region. The gas and stellar-velocity maps both show rotation patterns consistent with the large-scale rotation of the galaxy. However, the gaseous and stellar kinematics show deviations from pure disk rotation, which suggest streaming motions in the central 〈 200 pc and a velocity twist at the location of the ring which indicates deviations in disk and ring rotation velocities in accordance with published CO kinematics. We detect a blueshifted emission line split in Paα, associated with the nuclear region only. We investigate the star-formation properties of the hot spots in the circumnuclear ring which have starburst ages of ≲10 Myr and find indications for an age gradient on the western side of the ring. In addition, our high-resolution data reveal further substructure within this ring which also shows enhanced star forming activity close to the nucleus.

Beschreibung: We present our near-infrared, integral-field spectroscopy observations of the central 550 × 550 pc2 (10″ × 10″) of the local galaxy NGC 1672. Our aim is to investigate the morphology and kinematics of gas and stars to probe evidence for feeding and feedback phenomena. For this purpose the near-infrared wavelength regime and integral-field unit technique provide a vast amount of useful information. The narrow emission line ratios suggest that the galaxy hosts a low-luminosity active galactic nucleus. From the MBH − σ* relation, we find a black hole mass of a few 107 M⊙. The total reservoir of hot molecular and ionised gas is estimated, using flux of H2 and Brγ emission lines, to be 258 M⊙ and 2.3 × 106 M⊙ respectively. The most striking feature in the emission line flux maps is the star-forming ring at a radius of ∼3″. The stellar and gaseous kinematics both show a rotation pattern in a disc that is blue-shifted in the north-west and red-shifted in the south-east. However, unlike the stellar kinematics, gas kinematics show various complexities, such as higher amplitudes in the central region (within the star-forming ring). The molecular gas velocity-field map shows deviations from pure disc motion in the form of an S-shaped zero-velocity line. In particular the position angle of the zero-velocity line changes in the central arcsecond, resembling the decoupled nuclear disc or molecular torus found in CO(3–2). There is an offset of 0.″5 between the nuclear continuum barycentre and kinematic centre of molecular gas towards the north-west. The velocity field of Brγ emitting gas on the other hand, is highly red-shifted in the centre and offset from the continuum emission peak by about 1″. Investigating the spectra of this region we detect a doubled-horn Brγ emission line in the nucleus and north-west. This region is also luminous in radio 3 cm emission connecting the nucleus to the star-forming ring.

Beschreibung: Gas inflow processes in the vicinity of galactic nuclei play a crucial role in galaxy evolution and supermassive black hole growth. Exploring the central kiloparsec of galaxies is essential to shed more light on this subject. We present near-infrared H- and K-band results of the nuclear region of the nearby galaxy NGC 1326, observed with the integral-field spectrograph SINFONI mounted on the Very Large Telescope. The field of view covers 9″ × 9″ (650 × 650 pc2). Our work is concentrated on excitation conditions, morphology, and stellar content. The nucleus of NGC 1326 was classified as a LINER, however in our data we observed an absence of ionised gas emission in the central r ∼ 3″. We studied the morphology by analysing the distribution of ionised and molecular gas, and thereby detected an elliptically shaped, circum-nuclear star-forming ring at a mean radius of 300 pc. We estimate the starburst regions in the ring to be young with dominating ages of 〈 10 Myr. The molecular gas distribution also reveals an elongated east to west central structure about 3″ in radius, where gas is excited by slow or mild shock mechanisms. We calculate the ionised gas mass of 8 × 105 M⊙ completely concentrated in the nuclear ring and the warm molecular gas mass of 187 M⊙, from which half is concentrated in the ring and the other half in the elongated central structure. The stellar velocity fields show pure rotation in the plane of the galaxy. The gas velocity fields show similar rotation in the ring, but in the central elongated H2 structure they show much higher amplitudes and indications of further deviation from the stellar rotation in the central 1″ aperture. We suggest that the central 6″ elongated H2 structure might be a fast-rotating central disc. The CO(3–2) emission observations with the Atacama Large Millimeter/submillimeter Array reveal a central 1″ torus. In the central 1″ of the H2 velocity field and residual maps, we find indications for a further decoupled structure closer to a nuclear disc, which could be identified with the torus surrounding the supermassive black hole.