The nuclear gas disk of NGC 1566 dissected by SINFONI and ALMA

Abstract

We present the results of near-infrared (NIR) H-and K-band European Southern Observatory SINFONI integral field spectroscopy (IFS) of the Seyfert galaxy NGC 1566. We investigate the central kpc of this nearby galaxy, concentrating on excitation conditions, morphology, and stellar content. NGC 1566 was selected from our NUGA (-south) sample and is a ringed, spiral galaxy with a stellar bar in north-south direction (PA ∼ 5• ). The galaxy inhibits a very active Seyfert 1 nucleus but narrow line ratios from optical observations in the nuclear region are similar to Seyfert 2 galaxies. The recent strong activity phase, as inferred from strong variablity in X-ray to IR wavelengths, makes NGC 1566 an ideal candidate to look for feeding and feedback of a supermassive black hole. We present emission and absorption line measurements in the central kpc of NGC 1566. Broad and narrow Brγ lines were detected. The detection of a broad Brγ component is a clear sign of a supermassive black hole in the center. Blackbody emission temperatures of ∼1000 K are indicative of a hot dust component, the torus, in the nuclear region. The molecular hydrogen lines, hydrogen recombination lines, and [Fe ] indicate that the excitation at the center is coming from an AGN. The central region is predominantly inhabited by molecular gas, dust, and an old K-M type giant stellar population. The molecular gas and stellar velocity maps both show a rotation pattern. The molecular gas velocity field shows a perturbation toward the center that is typical for bars or spiral density waves. The molecular gas species of warm H 2 (1−0)S(1) and cold 12 CO(3−2) gas trace a nuclear gas disk of about 3 in radius with a nuclear spiral reaching toward the nucleus. From the equivalent width of H 2 (1−0)S(1) a molecular ring with r 3 can be inferred. This spiral seems to be an instrument that allows gas to fall toward the nucleus down to <50 pc scales. The excitation of molecular hydrogen in the nuclear gas disk is not clear, but diagnostic diagrams show a distinction between the nuclear region and a <9 Myr old star-forming region at the southwestern spiral arm. Gas that might be shocked is detected ≈2 from the center, which is visible in dispersion maps of H 2 (1−0)S(1) and 12 CO(3−2) and in the 0.87 mm continuum.

The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

“…NGC 1566 is shown to host a low-luminosity AGN (Combes et al 2014) with a star-forming ring at 1.7 kpc (Smajić et al 2015). We acknowledge that the distance of NGC 1566 is uncertain in the literature; in this work, we adopt the value of 13.2 Mpc, as reported in Calzetti et al (2015).…”

Near-infrared observations of star formation and gas flows in the NUGA galaxy NGC 1365

“…The observations of these galaxies with integral-field spectroscopy in the near-infrared (NIR) are complementary to the millimeter data (e.g., NGC 1433NGC , 1566NGC , and 1808Smajić et al 2014Smajić et al , 2015Busch et al 2017). The NIR data reveal informa-Article number, page 1 of 20 arXiv:1901.06241v1 [astro-ph.GA] 18 Jan 2019 A&A proofs: manuscript no.…”

WISDOM project – I. Black hole mass measurement using molecular gas kinematics in NGC 3665

“…As for ionised gas, molecular gas can in principle be affected by non-gravitational forces and turbulence (e.g. García-Burillo et al 2003;Smajić et al 2015), although in practice (giant) molecular clouds tend to move ballistically over much of their orbits, and molecular gas observations are unaffected by dust. Of course, some galaxies have no molecular gas detected (as is the case for many early-type galaxies; Young et al 2011), and others none in their very centre (Helfer et al 2003;Alatalo et al 2013), but this method has enormous potential.…”