arXiv subjects

H. R. Schmitt

Publications and source records attributed to H. R. Schmitt.

60 records · Page 4Linked to original sources

arXiv2000

Jet directions in Seyfert galaxies

We present the study of the relative angle between the accretion disk (or radio jet) and the galaxy disk for a sample of Seyfert galaxies selected from a mostly isotropic property, the 60$μ$m flux. For each galaxy we have a pair of points ($i$,$δ$), which are the inclination of the galaxy relative to the line of sight and the angle between the jet projected into the plane of the sky and the host galaxy major axis, respectively. This data is combined with a statistical technique to determine the distribution of $β$ angles {\it in 3 dimensions}, the angle between the jet and the host galaxy plane axis. The analysis of the data, not differentiating between Seyfert 1's and 2's, showed that the observed distribution of $i$ and $δ$ values can be well represented by a homogeneous $β-$distribution in the range $0^{\circ}\leqβ\leq90^{\circ}$. However, when we distinguished between Seyfert 1's and 2's, the models could not represent Seyfert 1's adequately. It was necessary to introduce viewing angle restrictions, that a galaxy can only be recognized as a Seyfert 1 if the angle between the jet and the line of sight ($|ϕ|$) is smaller than a given angle $ϕ_c$ and that the galaxy inclination $i$ is smaller than an angle $i_c$, in order to have statistically acceptable models. This is a direct and independent confirmation of the underlying concepts of the Unified Model. We discuss several ways to explain the misalignment between the accretion disk axis and the host galaxy disk axis.

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arXiv2000

Jet directions in Seyfert galaxies: B and I imaging data

We present the results of broad-band B and I imaging observations for a sample of 88 Seyfert galaxies (29 Seyfert 1's and 59 Seyfert 2's), selected from a mostly isotropic property, the flux at 60$μ$m. We also present the B and I imaging results for an additional sample of 20 Seyfert galaxies (7 Seyfert 1's and 13 Seyfert 2's), selected from the literature and known to have extended radio emission. The I band images are fitted with ellipses to determine the position angle and ellipticity of the host galaxy major axis. This information will be used in a future paper, combined with information from radio observations, to study the orientation of radio jets relative to the plane of their host galaxies (Kinney et al. 2000). Here we present surface brightness profiles and magnitudes in the B and I bands, as well as mean ellipticities and major axis position angles.

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arXiv1999

Direct measurement of the jet geometry in Seyfert galaxies

We demonstrate that, by combining optical, radio and X-ray observations of a Seyfert, it is possible to provide a direct measurement of the angle $β$ between the direction of the radio jet and the normal to the plane of the spiral host galaxy. To do so, we make the assumptions that the inner radio jet is perpendicular to the X-ray observed inner accretion disk, and that the observed jet (or the stronger component, if the jet is two-sided) is physically closer to Earth than the plane of the galaxy. We draw attention to the possibility of measurement producing a result which is not self-consistent, in which case for that galaxy, one of the assumptions must fail.

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arXiv1998

The Nature of the UV-Optical Continuum in Seyfert 2 Galaxies

The nature of the UV-Optical continuum in Seyfert 2 galaxies is a matter of current debate, fundamental to which is the issue of characterizing and quantifying the stellar population contribution to the nuclear spectra. Using high S/N long-slit spectroscopy of a sample of 20 Seyfert 2 galaxies, we have applied a novel approach to investigate the nuclear stellar population in these galaxies. Our main results are: (1) the stellar populations in Seyfert 2 galaxies are varied, and in most cases cannot be adequately represented by an elliptical galaxy template, as done in previous works; (2) the central kpc of most Seyfert 2's contain substantially larger proportions of 100 Myr stars than either elliptical galaxies or normal spirals of the same Hubble type. One important consequence of our findings is that the controversial nature of the so called ``second'' featureless continuum (FC2) in Seyfert 2's is most likely a result of inadequate evaluation of the stellar population.

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arXiv1997

The Spectral Energy Distribution of Normal, Starburst and Active Galaxies

We present the results of an extensive literature search of multiwavelength data for a sample of 59 galaxies, consisting of 26 Starbursts, 15 Seyfert 2's, 5 LINER's, 6 normal spirals and 7 normal elliptical galaxies. The data include soft X-ray fluxes, ultraviolet and optical spectra, near, mid/far infrared photometry and radio measurements, selected to match as closely as possible the IUE aperture (10" X 20"). The galaxies are separated into 6 groups with similar characteristics, namely, Ellipticals, Spirals, LINER's, Seyfert 2's, Starbursts of Low and High reddening, for which we create average spectral energy distributions (SED). The individual groups SED's are normalized to the $λ$7000Åflux and compared, looking for similarities and differences among them.The bolometric fluxes of different types of galaxies were calculated integrating their SED's. These values are compared with individual waveband flux densities, in order to determine the wavebands which contribute most to the bolometric flux. Linear regressions were performed between the bolometric and individual band fluxes for each kind of galaxy. These fits can be used in the calculation of the bolometric flux for other objects of similar activity type, but with reduced waveband information. We have also collected multiwavelength data for 4 HII regions, a thermal supernova remnant, and a non-thermal supernova remnant (SNR), which are compared with the Starburst SED's.

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arXiv1996

A Comparison of Radio Axis with Host Galaxy Plane Axis in Seyfert Galaxies

We use the radio axis as an indicator of the orientation of the obscuring torus in Seyfert galaxies, and analyze the difference between the position angles of extended radio structures and host galaxy major axis of Seyfert 1 and Seyfert 2 galaxies. We find that Seyfert 1's are less likely to have extended radio structures along the host galaxy major axis, while Seyfert 2's have these structures distributed in most directions. We also find a zone of avoidance in the distribution of position angles; both Seyfert 1's and Seyfert 2's seem to avoid close alignment between the radio axis and the host galaxy plane axis. These results are analyzed from the point of view of a model in which Seyfert 1's have their obscuring torus axis aligned preferentially along the host galaxy disk axis, and Seyfert 2's have their torus axis laying at an intermediate angle between the galaxy disk and its axis.

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