A Hidden Broad-Line Region in the Weak Seyfert 2 Galaxy NGC 788

We have detected a broad H alpha emission line in the polarized flux spectrum of the Seyfert 2 galaxy NGC 788, indicating that it contains an obscured Seyfert 1 nucleus. While such features have been observed in ~15 other Seyfert 2s, this example is unusual because it has a higher fraction of galaxy starlight in its spectrum, a lower average measured polarization, and a significantly lower radio luminosity than other hidden Seyfert 1s discovered to date. This demonstrates that polarized broad-line regions can be detected in relatively weak classical Seyfert 2s, and illustrates why well-defined, reasonably complete spectropolarimetric surveys at H alpha are necessary in order to assess whether or not all Seyfert 2s are obscured Seyfert 1s.Comment: 10 pages using (AASTEX) aaspp4.sty and 4 postscript figures. Publications of the Astronomical Society of the Pacific, Research Notes, in pres

X-ray Emission from the Weak-lined T Tauri Binary System KH 15D

The unique eclipsing, weak-lined T Tauri star KH 15D has been detected as an X-ray source in a 95.7 ks exposure from the Chandra X-ray Observatory archives. A maximum X-ray luminosity of 1.5 x 10^{29} erg s$^{-1}$ is derived in the 0.5--8 keV band, corresponding to L_{X}/L_bol = 7.5 x 10^{-5}. Comparison with samples of stars of similar effective temperature in NGC 2264 and in the Orion Nebula Cluster shows that this is about an order of magnitude low for a typical star of its mass and age. We argue that the relatively low luminosity cannot be attributed to absorption along the line of sight but implies a real deficiency in X-ray production. Possible causes for this are considered in the context of a recently proposed eccentric binary model for KH 15D. In particular, we note that the visible component rotates rather slowly for a weak-lined T Tauri star and has possibly been pseudosynchronized by tidal interaction with the primary near periastron

Polarized Broad H-alpha Emission from the LINER Nucleus of NGC 1052

Optical spectropolarimetry of the nucleus of the LINER NGC 1052, obtained at the Keck Observatory, reveals a rise in polarization in the wings of the H-alpha line profile. The polarization vector of H-alpha is offset by 67 degrees from the parsec-scale radio axis and by 83 degrees from the kiloparsec-scale radio axis, roughly in accord with expectations for scattering within the opening cone of an obscuring torus. The broad component of H-alpha has FWHM ~ 2100 km/s in total flux and FWHM ~ 5000 km/s in polarized light. Scattering by electrons is the mechanism most likely responsible for this broadening, and we find T_e ~ 10^5 K for the scattering medium, similar to values observed in Seyfert 2 nuclei. This is the first detection of a polarized broad emission line in a LINER, demonstrating that unified models of active galactic nuclei are applicable to at least some LINERs.Comment: 6 pages, 2 figures, prepared using the emulateapj style file, accepted for publication in The Astrophysical Journal Letter

Polarized Broad-Line Emission from Low-Luminosity Active Galactic Nuclei

In order to determine whether unified models of active galactic nuclei apply to low-luminosity objects, we have undertaken a spectropolarimetric survey of of LINERs and Seyfert nuclei at the Keck Observatory. The 14 objects observed have a median H-alpha luminosity of 8x10^{39} erg/s, well below the typical value of ~10^{41} erg/s for Markarian Seyfert nuclei. Polarized broad H-alpha emission is detected in three LINERs: NGC 315, NGC 1052, and NGC 4261. Each of these is an elliptical galaxy with a double-sided radio jet, and the emission-line polarization in each case is oriented roughly perpendicular to the jet axis, as expected for the obscuring torus model. NGC 4261 and NGC 315 are known to contain dusty circumnuclear disks, which may be the outer extensions of the obscuring tori. The detection of polarized broad-line emission suggests that these objects are nearby, low-luminosity analogs of obscured quasars residing in narrow-line radio galaxies. The nuclear continuum of the low-luminosity Seyfert 1 galaxy NGC 4395 is polarized at p = 0.67%, possibly the result of an electron scattering region near the nucleus. Continuum polarization is detected in other objects, with a median level of p = 0.36% over 5100-6100 A, but in most cases this is likely to be the result of transmission through foreground dust. The lack of significant broad-line polarization in most type 1 LINERs is consistent with the hypothesis that we view the broad-line regions of these objects directly, rather than in scattered light.Comment: 28 pages, including 3 tables and 16 figures. Uses the emulateapj latex style file. Accepted for publication in The Astrophysical Journa

The 3-53 keV Spectrum of the Quasar 1508+5714: X-rays from z = 4.3

We present a high-quality X-ray spectrum in the 3--53 keV rest-frame band of the radio-loud quasar 1508+5714, by far the brightest known X-ray source at z > 4. A simple power-law model with an absorption column density equal to the Galactic value in the direction of the source provides an excellent and fully adequate fit to the data; the measured power-law photon index Gamma = 1.42 (+0.13,-0.10). Upper limits to Fe K alpha line emission and Compton-reflection components are derived. We offer evidence for both X-ray and radio variability in this object and provide the first contemporaneous radio spectrum (alpha = -0.25). The data are all consistent with a picture in which the emission from this source is dominated by a relativistically beamed component in both the X-ray and radio bands.Comment: 8 pages, TeX, 2 postscript figures; to appear in ApJ Letter

The Nuclear Spectral Energy Distribution of NGC 4395, The Least Luminous Type 1 Seyfert Galaxy

We present X-ray (ROSAT), infrared, and radio observations of NGC 4395, which harbors the optically least luminous type 1 Seyfert nucleus discovered thus far. In combination with published optical and ultraviolet spectra, we have used these data to assemble the broadband spectral energy distribution (SED) of the galaxy's nucleus. Interestingly, the SED of NGC 4395 differs markedly from the SEDs of both quasars and typical low-luminosity active galactic nuclei, which may be a manifestation of the different physical conditions (i.e., black hole masses, accretion rates, and/or accretion modes) that exist in these objects. The nuclear X-ray source in NGC 4395 is variable and has an observed luminosity of just ~ 10^38 ergs/s. Although this emission could plausibly be associated with either a weak active nucleus or a bright stellar-mass binary system, the optical and ultraviolet emission-line properties of the nucleus strongly suggest that the X-rays arise from a classical AGN.Comment: Accepted for publication in PASP (July 1999), 17 pages, including 4 Postscript figure

"Hidden" Seyfert 2 Galaxies and the X-ray Background

Obscured active galactic nuclei, which are classified optically as type 2 (narrow-line) Seyfert galaxies in the local universe, are by far the most promising candidates for the origin of the hard (2-10 keV) X-ray background radiation. However, optical follow-up observations of faint X-ray sources in deep Chandra images have revealed surprising numbers of apparently normal galaxies at modest redshift. Such objects represent ~40-60% of the sources classified in deep Chandra surveys, raising the possibility that the X-ray galaxy population has evolved with cosmic time. Alternatively, most of the faint X-ray galaxies in question are so distant that their angular diameters are comparable to the slit widths used in ground-based spectroscopic observations; thus, their nuclear spectral features may be overwhelmed (``hidden'') by host-galaxy light. To test this hypothesis, we have obtained integrated spectra of a sample of nearby, well-studied Seyfert 2 galaxies. The data, which accurately simulate observations of distant Chandra sources, demonstrate convincingly that the defining spectral signatures of Seyfert 2s can be hidden by light from their host galaxies. In fact, 60% of the observed objects would not be classified as Seyfert 2s on the basis of their integrated spectra, similar to the fraction of faint X-ray sources identified with ``normal'' galaxies. Thus, the numbers of narrow-line active galaxies in deep Chandra surveys (and perhaps all ground-based spectroscopic surveys of distant galaxies) are likely to have been underestimated.Comment: 9 pages, including 1 figure. To appear in ApJ Letter

A Composite Seyfert 2 X-ray Spectrum: Implications for the Origin of the Cosmic X-ray Background

We present a composite 1-10 keV Seyfert 2 X-ray spectrum, derived from ASCA observations of a distance-limited sample of nearby galaxies. All 29 observed objects were detected. Above ~3 keV, the composite spectrum is inverted, confirming that Seyfert 2 galaxies as a class have the spectral properties necessary to explain the flat shape of the cosmic X-ray background spectrum. Integrating the composite spectrum over redshift, we find that the total emission from Seyfert 2 galaxies, combined with the expected contribution from unabsorbed type 1 objects, provides an excellent match to the spectrum and intensity of the hard X-ray background. The principal uncertainty in this procedure is the cosmic evolution of the Seyfert 2 X-ray luminosity function. Separate composite spectra for objects in our sample with and without polarized broad optical emission lines are also presented.Comment: 11 pages (AASTeX), including 3 figures. Accepted for publication in ApJ Letter