Rogemar A. Riffel

A 0.8-2.4 μm spectral atlas of active galactic nuclei

Aims. We present a near-infrared spectral atlas of 47 active galactic nuclei (AGN) of all degrees of activity in the wavelength interval of 0.8-2.4 � m, including the fluxes of the observed emission lines. We ana lyze the spectroscopic properties of the continuum and emission line spectra of the sources. Methods. In order to exclude aperture and seeing effects we used near-infrared spectroscopy in the short cross-dispersed mode (SXD, 0.8−2.4� m), taking the JHK-bands spectra simultaneously. Results. We present the most extensive NIR spectral atlas of AGN to date. This atlas offers a suitable database for studying the continuum and line emission properties of these objects in a region full of interesting features. The shape of the continuum of QSOs and Sy 1’s are similar, being essentially flat in the H and K bands, while a strong vari ation is found in the J band. In Seyfert 2 galaxies, the contin uum in the Fλ×λ space smoothly decreases in flux from 1.2� m redwards in almost all sources. In J, it smoothly rises bluewards in some sources, while in others a small decrease in flux is observed. The spectra are do minated by strong emission features of Hi, Hei, Heii, [Siii] and by conspicuous forbidden lines of low and high ionization species. Molecular lines of H2 are common features of most objects. The absence of Oi and Feii lines in Seyfert 2 galaxies and the smaller FWHM of these lines relative to that of Hi in the Seyfert 1 give observational support to the fact that they are formed in the outermost portion of the broad-line region. The[Pii] and coronal lines are detected for all degrees of activity. The [Feii] 12570A/16436A line ratio becomes a reliable reddening indicator for the narrow-line region of Seyfert galaxies.

Feeding versus feedback in NGC 4151 probed with Gemini NIFS – II. Kinematics

We have used the Gemini Near-infrared Integral Field Spectrograph (NIFS) to map the gas kinematics of the inner ∼200 x 500 pc 2 of the Seyfert galaxy NGC 4151 in the Z, J, H and K bands at a resolving power of ≥5000 and spatial resolution of ∼8 pc. The ionized gas emission is most extended along the known ionization bi-cone at position angle PA = 60°-240°, but is observed also along its equatorial plane. This indicates that the active galactic nucleus (AGN) ionizes gas beyond the borders of the bi-cone, within a sphere with ≈1 arcsec radius around the nucleus. The ionized gas has three kinematic components: (1) one observed at the systemic velocity and interpreted as originating in the galactic disc; (2) one outflowing along the bi-cone, with line-of-sight velocities between -600 and 600 km s ―1 and strongest emission at ±(100―300) km s ―1 ; and (3) another component due to the interaction of the radio jet with ambient gas. The radio jet (at PA = 75°-255°) is not aligned with the narrow-line region (NLR) and produces flux enhancements mostly observed at the systemic velocity, suggesting that the jet is launched close to the plane of the galaxy (approximately plane of the sky). The mass outflow rate, estimated to be ≈ 1 M ⊙ yr ―1 along each cone, exceeds the inferred black hole accretion rate by a factor of ∼100. This can be understood if the NLR is formed mostly by entrained gas from the circumnuclear interstellar medium by an outflow probably originating in the accretion disc. This flow represents feedback from the AGN, estimated to release a kinetic power of Ė ≈ 2.4 x 10 41 erg s ―1 , which is only ∼0.3 per cent of the bolometric luminosity of the AGN. There is no evidence in our data for the gradual acceleration followed by gradual deceleration proposed by previous modelling of the [O III] emitting gas. Our data allow the possibility that the NLR clouds are accelerated close to the nucleus (within 0.1 arcsec, which corresponds to ≈7 pc at the galaxy) after which the flow moves at essentially constant velocity (≈600 km s ―1 ), being consistent with near-infrared emission arising predominantly from the interaction of the outflow with gas in the galactic disc. The molecular gas exhibits distinct kinematics relative to the ionized gas. Its emission arises in extended regions approximately perpendicular to the axis of the bi-cone and along the axis of the galaxys stellar bar, avoiding the innermost ionized regions. It does not show an outflowing component, being observed only at velocities very close to systemic, and is thus consistent with an origin in the galactic plane. This hot molecular gas may only be the tracer of a larger reservoir of colder gas which represents the AGN feeding.

Streaming Motions toward the Supermassive Black Hole in NGC 1097

We have used GMOS-IFU and high-resolution HST-ACS observations to map, in unprecedented detail, the gas velocity field and structure within the 0.7 kpc circumnuclear ring of the SBb LINER/Seyfert 1 galaxy NGC 1097. We find clear evidence of radial streaming motions associated with spiral structures leading to the unresolved (<3.5 pc) nucleus, which we interpret as part of the fueling chain by which gas is transported to the nuclear starburst and supermassive black hole.

Feeding versus feedback in NGC 4151 probed with Gemini NIFS – I. Excitation

We have used the Gemini Near-infrared Integral Field Spectrograph (NIFS) to map the emission-line intensity distributions and ratios in the narrow-line region (NLR) of the Seyfert galaxy NGC 4151 in the Z, J, H and K bands at a resolving power ≥5000, covering the inner ≈200 x 300 pc of the galaxy at a spatial resolution of ≈8 pc. We present intensity distributions in 14 emission lines, which show three distinct behaviours. (1) Most of the ionized gas intensity distributions are extended to ≈1100 pc from the nucleus along the region covered by the known biconical outflow (position angle, PA = 60/240°, NE-SW), consistent with an origin in the outflow; while the recombination lines show intensity profiles which decrease with distance r from the nucleus as I ∝ r -1 , most of the forbidden lines present a flat intensity profile (I ∝ r 0 ) or even increasing with distance from the nucleus towards the border of the NLR. (2) The H 2 emission lines show completely distinct intensity distributions, which avoid the region of the bicone, extending from ≈10 to ≈60 pc from the nucleus approximately along the large-scale bar, almost perpendicular to the bicone axis. This morphology supports an origin for the H 2 -emitting gas in the galaxy plane. (3) The coronal lines show a steep intensity profile, described by I ∝ r -2 ; the emission is clearly resolved only in the case of [Si VII], consistent with an origin in the inner NLR. Using the line-ratio maps [Fe II] 1.644/1.257 and Pa β/Br γ, we obtain an average reddening of E(B - V) ≈ 0.5 along the NLR and E(B - V) ≥ 1 at the nucleus. Our line-ratio map [Pe II] 1.257 μm/[P II] 1.189 μm of the NLR of NGC4151 is the first such map of an extragalactic source. Together with the [Fe II]/Paβ map, these line ratios correlate with the radio intensity distribution, mapping the effects of shocks produced by the radio jet on the NLR. These shocks probably release the Fe locked in grains and produce an enhancement of the [Fe II] emission at ≈1 arcsec from the nucleus. At these regions, we obtain electron densities N e ≈4000 cm -3 and temperatures T e ≈ 15 000 K for the [Fe II]-emitting gas. For the H 2 -emitting gas, we obtain much lower temperatures of T exc ≈ 2100 K and conclude that the gas is in thermal equilibrium. The heating necessary to excite the molecule may be due to X-rays escaping perpendicular to the cone (through the nuclear torus, if there is one) or to shocks probably produced by the accretion flow previously observed along the large-scale bar. The distinct intensity distributions and physical properties of the ionized and molecular gas, as well as their locations, the former along the outflowing cone, and the latter in the galaxy plane surrounding the nucleus, suggest that the H 2 -emitting gas traces the active galactic nuclei feeding, while the ionized gas traces its feedback.

AGN-starburst connection in NGC 7582: Gemini near-infrared spectrograph integral field unit observations

We analyse two-dimensional near-infrared K-band spectra from the inner 660 × 315 pc 2 of the Seyfert galaxy NGC 7582 obtained with the Gemini near-infrared spectrograph integral field unit at a spatial resolution of ≈50 pc and spectral resolving power R ≈ 5900. The nucleus harbours an unresolved source well reproduced by a blackbody of temperature T ≈ 1050 K, which we attribute to emission by circumnuclear dust located closer than 25 pc from the nucleus, with a total mass of ≈3 × 10 −3 M� . Surrounding the nucleus, we observe a ring of active star formation, apparently in the Galactic plane, with a radius of ≈190 pc, an age of ≈5 Myr and a total mass of ionized gas of ≈3 × 10 6 M� . The radiation of the young stars in the ring accounts for at least 80 per cent of the ionization observed in the Brγ emitting gas, the remaining being due to the radiation emitted by the active nucleus. The stellar kinematics was derived using the CO absorption band at 2.29 μm and reveals: (i) a distorted rotation pattern in the radial velocity field with kinematic centre apparently displaced from the nuclear source by a few tens of parsec; (ii) a high-velocity dispersion in the bulge of σ ∗ = 170 km s −1 and (iii) a partial ring of σ ∗ = 50 km s −1 , located close to the Brγ emitting ring, but displaced by ≈50 pc towards the nucleus, interpreted as due to stars formed from cold gas in a previous burst of star formation. The kinematics of the ionized gas shows a similar rotation pattern to that of the stars, plus a blueshifted component with velocities ≥ 100 km s −1 interpreted as due to an outflow along the ionization cone, which was partially covered by our observations. The mass outflow rate in the ionized gas was estimated as u

Compact molecular disc and ionized gas outflows within 350 pc of the active nucleus of Mrk 1066

We present stellar and gaseous kinematics of the inner ≈350-pc radius of the Seyfert galaxy Mrk 1066 derived from J and K 1 bands data obtained with the Geminis Near-Infrared Integral Field Spectrograph (NIFS) at a spatial resolution of ≈35 pc. The stellar velocity field is dominated by rotation in the galaxy plane but shows an S-shape distortion along the galaxy minor axis which seems to be due to an oval structure seen in an optical continuum image. Along this oval, between 170 and 280 pc from the nucleus we find a partial ring of low σ * (≈50 km s -1 ) attributed to an intermediate-age stellar population. The velocity dispersion of the stellar bulge (σ * ≈ 90 km s -1 ) implies a supermassive black hole mass of ≈5.4 x 10 6 M ⊙ . From measurements of the emission-line fluxes and profiles ([P II]λ1.1886 μm, [Fe II]λ1.2570 μm, Paβ and H 2 λ2.1218 μm), we have constructed maps for the gas centroid velocity, velocity dispersion as well as channel maps. The velocity fields for all emission lines are dominated by a similar rotation pattern to that observed for the stars, but are distorted by the presence of two structures: (i) a compact rotating disc with radius r ≈ 70 pc; (ii) outflows along the radio jet which is oriented approximately along the galaxy major axis. The compact rotating disc is more conspicuous in the H 2 emitting gas, which presents the smallest σ values (≤70 km s -1 ) and most clear rotation pattern, supporting a location in the galaxy plane. We estimate a gas mass for the disc of ~10 7 M ⊙ . The H 2 kinematics further suggests that the nuclear disc is being fed by gas coming from the outer regions. The outflow is more conspicuous in the [Fe II] emitting gas, which presents the highest σ values (up to 150 km s -1 ) and the highest blue and redshifts of up to 500 km s -1 , while the highest stellar rotation velocity is only ≈ 130 km s -1 . We estimate a mass-outflow rate in ionized gas of ≈ 6 x 10 -2 M ⊙ yr -1 . The derived kinematics for the emitting gas is similar to that observed in previous studies supporting that the H 2 is a tracer of the active galactic nucleus feeding and the [Fe II] of its feedback.

Feeding Versus Feedback in AGNs from Near-Infrared IFU Observations: The Case of Mrk 79

We have mapped the gaseous kinematics and the emission-line flux distributions and ratios from the inner≈ 680 pc radius of the Seyfert 1 galaxy Mrk 79, using two-dimensional (2D) near-IR J− and Kl−band spectra obtained with the Gemini instrument NIFS at a spatial resolution of≈100 pc and velocity resolution of≈ 40 km s −1 . The molecular hydrogen H2 flux distribution presents two spiral arms extending by ≈ 700 pc, one to the north and another to the south of the nucleus, with an excitation indicating he ating by X-rays from the central source. The low velocity dispersion (σ≈ 50km s −1 ) and rotation pattern supports a location of the H2 gas in the disk of the galaxy. Blueshifts observed along the spiral arm in the far side of the galaxy and redshifts in the spiral arm in the near s ide, suggest that the spiral arms are feeding channels of H2 to the inner 200 pc. From channel maps along the H2λ2.1218µm emission-line profile we estimate a mass inflow rate of ˙ MH2 ≈ 4× 10 −3 M⊙ yr −1 , which is one order of magnitude smaller than the mass accretion rate necessary to power the AGN of Mrk 79.The emission from the ionized gas (traced by Paβ and [Feii]λ1.2570µm emission lines) is correlated with the radio jet and with the narrow-b and [Oiii] flux distribution. Its kinematics shows both rotation and outflows to the north and s outh of the nucleus. The ionized gas mass outflow rate through a cross section with radius ≈ 320 pc located at a distance of ≈455 pc from the nucleus is ˙ Mout ≈ 3.5 M⊙ yr −1 , which is much larger than the AGN mass accretion rate, indicating that most of the outflowing gas or iginates in the interstellar medium surrounding the galaxy nucleus, which is pushed away by a nuclear jet.

Near-infrared dust and line emission from the central region of Mrk 1066: constraints from Gemini NIFS

We present integral field spectroscopy of the inner 700 x 700pc 2 of the Seyfert galaxy Mrk 1066 obtained with Geminis Near-Infrared Integral Field Spectrograph (NIFS) at a spatial resolution of ≈35 pc. This high spatial resolution allowed us to observe, for the first time in this galaxy, an unresolved dust concentration with mass ~1.4 x 10 -2 M ☉ . This unresolved concentration, with emission well reproduced by a blackbody with temperature ~830 K, is possibly part of the nuclear dusty torus. We compared maps of emission-line flux distributions and ratios with a 3.6 cm radio-continuum image and [O III] image in order to investigate the origin of the near-infrared emission. The emission-line fluxes are elongated in PA = 135°/315° in agreement with the [O m] and radio images and, except for the H lines, are brighter to the north-west than to the south-east. This close association with the radio hot spot implies that at least part of the emitting gas is co-spatial with the radio outflow. The H emission is stronger to the south-east, where we find a large region of star-formation. The strong correlation between the radio emission and the highest emission-line fluxes indicates that the radio jet plays a fundamental role at these intensity levels. At lower emission-line fluxes this correlation disappears suggesting a contribution from the plane of the galaxy to the observed emission. The H 2 flux is more uniformly distributed and has an excitation temperature of ≈2100 K. Its origin appears to be circum-nuclear gas heated by X-rays from the central active nucleus. The [Fe II] emission also is consistent with X-ray heating, but its spatial correlation with the radio jet and [O III] emission indicates additional emission due to excitation and/or abundance changes caused by shocks in the radio jet. The coronal-line emission of [Ca VIII] and [S IX] is unresolved by our observations indicating a distribution within 18 pc from the nucleus. The reddening map obtained via the Paβ/Brγ line ratio ranges from E(B - V) ≈ 0 to 1.7 with the highest values defining a S-shaped structure along PA ≈ 135°/315°. The emission-line ratios are Seyfert-like within the ionization cone indicating that the line emission is powered by the central active nucleus in these locations. Low ionization regions are observed away from the ionization cone, and may be powered by the diffuse radiation field which filters through the ionization cone walls. Two regions at 0.5 arcsec south-east and at 1 arcsec north-west of the nucleus show starburst-like line ratios, co-spatial with an enhancement in the emission of the H lines. We attribute this change to additional emission from star-forming regions. The mass of ionized gas is M H II ≈ 1.7 × 10 7 M ☉ and that of hot molecular gas is M H2 ≈ 3.3 x 10 3 M ☉ .

The first detection of near-infrared CN bands in active galactic nuclei:signature of star formation

We present the first detection of the near-infrared CN absorption band in the nuclear spectra of active galactic nuclei (AGNs). This feature is a recent star formation tracer, being particularly strong in carbon stars. The equivalent width of the CN line correlates with that of the CO at 2.3 μm as expected in stellar populations (SPs) with ages between ~0.2 and ~2 Gyr. The presence of the 1.1 μm CN band in the spectra of the sources is taken as unambiguous evidence of the presence of young/intermediate SPs close to the central source of the AGNs. Near-infrared bands can be powerful age indicators for star formation connected to AGNs, the understanding of which is crucial in the context of galaxy formation and AGN feedback.

THE BLACK HOLE MASS OF NGC 4151. II. STELLAR DYNAMICAL MEASUREMENT FROM NEAR-INFRARED INTEGRAL FIELD SPECTROSCOPY

We present a revised measurement of the mass of the central black hole (Mbh) in the Seyfert 1 galaxy NGC 4151. The new stellar dynamical mass measurement is derived by applying an axisymmetric orbit-superposition code to near-infrared integral field data obtained using adaptive optics with the Gemini NIFS spectrograph. When our models attempt to fit both the NIFS kinematics and additional low spatial resolution kinematics, our results depend sensitively on how chi-squared is computed--probably a consequence of complex bar kinematics that manifest immediately outside the nuclear region. The most robust results are obtained when only the high spatial resolution kinematic constraints in the nuclear region are included in the fit. Our best estimates for the BH mass and H-band mass-to-light ratio are Mbh~(3.76+/-1.15)E7 Msun (1-sigma error) and M/L(H-band)~0.34+/-0.03 Msun/Lsun (3-sigma error), respectively (the quoted errors reflect the model uncertainties). Our BH mass measurement is consistent with estimates from both reverberation mapping (3.57[+0.45/-0.37]E7 Msun) and gas kinematics (3.0[+0.75/-2.2]E7 Msun; 1-sigma errors), and our best-fit mass-to-light ratio is consistent with the photometric estimate of M/L(H-band)=0.4+/-0.2 Msun/Lsun. The NIFS kinematics give a central bulge velocity dispersion sigma_c=116+/-3 km/s, bringing this object slightly closer to the M-sigma relation for quiescent galaxies. Although NGC 4151 is one of only a few Seyfert 1 galaxies in which it is possible to obtain a direct dynamical BH mass measurement--and thus, an independent calibration of the reverberation mapping mass scale--the complex bar kinematics makes it less than ideally suited for this purpose.