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Register a new userThe nuclear regions of NGC 7582 from [NeII] spectroscopy at 12.8 microns - an estimate of the black hole mass
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M. Wold
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We present a high-resolution (R~16,000) spectrum and a narrow-band image centered on the [NeII]12.8 micron line of the central kpc region of the starburst/Seyfert2 galaxy NGC 7582. The galaxy has a rotating circum-nuclear starburst disk, shown at great detail at a diffraction-limited resolution of 0.4 arcsec. The high spatial resolution allows us to probe the dynamics of the [NeII] gas in the nuclear regions, and to estimate the mass of the central black hole. We construct models of gas disks rotating in the combined gravitational potential from the stellar bulge and a central black hole, and derive a black hole mass of 5.5 x 10^7 solar masses with a 95% confidence interval of [3.6,8.1] x 10^7 solar masses. The black hole mass combined with stellar velocity dispersion measurements from the literature shows that the galaxy is consistent with the local M-sigma relation. This is the first time that a black hole mass in a galaxy except our own Milky Way system has been estimated from gas dynamics in the mid-infrared. We show that spatially resolved mid-infrared spectroscopy may be competitive with similar techniques in the optical and near-infrared, and may prove to be important for estimating black hole masses in galaxies with strong nuclear dust obscuration. The high spectral resolution allows us to determine the heliocentric systemic velocity of the galaxy to between 1614 and 1634 km/s. The mid-infrared image reveals several dense knots of dust-embedded star formation in the circum-nuclear disk, and we briefly discuss its morphology.
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We present the results of the spatial and spectral analysis of the deep (~200 ksec) Chandra HETG observation of the changing look AGN NGC7582. During this observation NGC7582 was in a highly obscured state. Therefore, we considered also a short Suzaku observation, which caught NGC7582 in a Compton thick state. This allows us to determine the underlying continuum and the amount of absorption ($N_H sim~1.2times10^{24}$ cm$^{-2}$). A wealth of emission lines are detected in the Chandra data, which allow us to map the structure of the circum-nuclear emitters. The high resolution spectrum reveals that the soft X-ray emission originates in a hybrid gas, which is ionized in part by the starforming activity and in part by the central AGN. The high resolution images confirm that the emitting region is inhomogeneous and extends up to a few hundred pc from the nuclear source. The X-ray images are more extended in the lower energy lines (Ne and Mg) than in the higher energy lines (Si, Fe), where the former are dominated by the collisionally ionised gas and the latter by the photoionized AGN emission. This is supported by the analysis of the He-like triplets. We deduce that a low density photoionized gas is responsible for the strong forbidden components, which is likely to originate from extended AGN Narrow Line Region gas at distances of 200-300 pc from the black hole. We also detected an absorption feature at ~ 6.7 keV consistent with the rest frame energy of the resonance absorption line from FeXXV, which traces the presence of a sub-parsec scale ionized absorber. The emerging picture is in agreement with our view of the circumnuclear gas in AGN, where the medium is clumpy and stratified in both density and ionization. These absorbers and emitters are located on different scales: from the sub-pc Broad Line Region gas out to the kpc scale of the galactic absorber.
Recent X-ray observations by Jiang et al. have identified an active galactic nucleus (AGN) in the bulgeless spiral galaxy NGC 3319, located just $14.3pm1.1,$Mpc away, and suggest the presence of an intermediate-mass black hole (IMBH; $10^2leq M_bullet/mathrm{M_{odot}}leq10^5$) if the Eddington ratios are as high as 3 to $3times10^{-3}$. In an effort to refine the black hole mass for this (currently) rare class of object, we have explored multiple black hole mass scaling relations, such as those involving the (not previously used) velocity dispersion, logarithmic spiral-arm pitch angle, total galaxy stellar mass, nuclear star cluster mass, rotational velocity, and colour of NGC 3319, to obtain ten mass estimates, of differing accuracy. We have calculated a mass of $3.14_{-2.20}^{+7.02}times10^4,mathrm{M_odot}$, with a confidence of 84% that it is $leq$$10^5,mathrm{M_odot}$, based on the combined probability density function from seven of these individual estimates. Our conservative approach excluded two black hole mass estimates (via the nuclear star cluster mass, and the fundamental plane of black hole activity $unicode{x2014}$ which only applies to black holes with low accretion rates) that were upper limits of $sim$$10^5,{rm M}_{odot}$, and it did not use the $M_bulletunicode{x2013}L_{rm 2-10,keV}$ relations prediction of $sim$$10^5,{rm M}_{odot}$. This target provides an exceptional opportunity to study an IMBH in AGN mode and advance our demographic knowledge of black holes. Furthermore, we introduce our novel method of meta-analysis as a beneficial technique for identifying new IMBH candidates by quantifying the probability that a galaxy possesses an IMBH.
The mass of a supermassive black hole ($M_mathrm{BH}$) is a fundamental property that can be obtained through observational methods. Constraining $M_mathrm{BH}$ through multiple methods for an individual galaxy is important for verifying the accuracy of different techniques, and for investigating the assumptions inherent in each method. NGC 4151 is one of those rare galaxies for which multiple methods can be used: stellar and gas dynamical modeling because of its proximity ($D=15.8pm0.4$ Mpc from Cepheids), and reverberation mapping because of its active accretion. In this work, we re-analyzed $H-$band integral field spectroscopy of the nucleus of NGC 4151 from Gemini NIFS, improving the analysis at several key steps. We then constructed a wide range of axisymmetric dynamical models with the new orbit-superposition code Forstand. One of our primary goals is to quantify the systematic uncertainties in $M_mathrm{BH}$ arising from different combinations of the deprojected density profile, inclination, intrinsic flattening, and mass-to-light ratio. As a consequence of uncertainties on the stellar luminosity profile arising from the presence of the AGN, our constraints on mbh are rather weak. Models with a steep central cusp are consistent with no black hole; however, in models with more moderate cusps, the black hole mass lies within the range of $0.25times10^7,M_odot lesssim M_mathrm{BH} lesssim 3times10^7,M_odot$. This measurement is somewhat smaller than the earlier analysis presented by Onken et al., but agrees with previous $M_mathrm{BH}$ values from gas dynamical modeling and reverberation mapping. Future dynamical modeling of reverberation data, as well as IFU observations with JWST, will aid in further constraining $M_mathrm{BH}$ in NGC 4151.
An intermediate-mass black hole (IMBH) was recently reported to reside in the centre of the Galactic globular cluster (GC) NGC 6624, based on timing observations of a millisecond pulsar (MSP) located near the cluster centre in projection. We present dynamical models with multiple mass components of NGC 6624 - without an IMBH - which successfully describe the surface brightness profile and proper motion kinematics from the Hubble Space Telescope (HST) and the stellar mass function at different distances from the cluster centre. The maximum line-of-sight acceleration at the position of the MSP accommodates the inferred acceleration of the MSP, as derived from its first period derivative. With discrete realizations of the models we show that the higher-order period derivatives - which were previously used to derive the IMBH mass - are due to passing stars and stellar remnants, as previously shown analytically in literature. We conclude that there is no need for an IMBH to explain the timing observations of this MSP.
We report on the discovery of several compact regions of mid-infrared emission in the starforming circum nuclear disk of the starburst/Seyfert2 galaxy NGC7582. The compact sources do not have counterparts in the optical and near-infrared, suggesting that they are deeply embedded in dust. We use the [NeII]12.8 micron line emission to estimate the emission measure of the ionized gas, which in turn is used to assess the number of ionizing photons. Two of the brighter sources are found to have ionizing fluxes of ~2.5x10^52, whereas the fainter ones have ~1x10^52 photons/s. Comparing with a one Myr old starburst, we derive stellar masses in the range (3-5)x10^5 Msun, and find that the number of O-stars in each compact source is typically (0.6-1.6)x10^3. We conclude that the compact mid-infrared sources are likely to be young, embedded star clusters, of which only a few are known so far. Our observation highlights the need for high resolution mid-infrared imaging to discover and study embedded star clusters in the proximity of active galactic nuclei.
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