We propose a scenario where blazars are classified as flat-spectrum radio quasars (FSRQs), BL Lacs, low synchrotron, or high synchrotron peaked objects according to a varying mix of the Doppler boosted radiation from the jet, the emission from the accretion disk, the broad line region, and the light from the host galaxy. In this framework the peak energy of the synchrotron power (ν S ) in blazars is independent of source type and of radio luminosity. We test this new approach, which builds upon unified schemes, using extensive Monte Carlo simulations and show that it can provide simple answers to a number of long-standing issues including, amongst others, the different cosmological evolution of BL Lacs selected in the radio and X-ray bands, the larger ν S peak values observed in BL Lacs, the fact that high synchrotron peaked blazars are always of the BL Lac type, and the existence of FSRQ/BL Lac transition objects. Objects so far classified as BL Lacs on the basis of their observed weak, or undetectable, emission lines are of two physically different classes: intrinsically weak lined objects, more common in X-ray selected samples, and heavily diluted broad lined sources, more frequent in radio selected samples, which explains some of the confusion in the literature. We also show that strong selection effects are the main cause of the diversity observed in radio and X-ray samples, and that the correlation between luminosity and ν S , that led to the proposal of the “blazar sequence”, is also a selection effect arising from the comparison of shallow radio and X-ray surveys, and to the fact that high ν S peak - high radio power objects have never been considered because their redshift is not measurable.

A simplified view of blazars: clearing the fog around long‐standing selection effects

We have obtained low-dispersion spectra of NGC 3227 with the Space Telescope Imaging Spectrograph (STIS) to study the intrinsic UV absorption and the reddening of the nucleus in this Seyfert 1 galaxy. The UV spectra show a wealth of absorption lines at the systemic redshift that span a wide range in ionization state (Mg I to N V). The equivalent widths of the lines are consistent with our earlier prediction that a "lukewarm absorber" (Te = 18,000 K at the ionized face) with a substantial column of gas (NH = 2 × 1021 cm-2) is present and likely responsible for the reddening of the nucleus. The lukewarm absorber is also responsible for most of the absorption in the X-rays at energies less than 1 keV, although a more highly ionized "warm absorber" is needed to account for the O VII and O VIII ionization edges. In addition, we require a small column (NH = 5 × 1019 cm-2) of cold gas to match the strengths of the neutral and singly ionized lines in the UV spectra. NGC 3227 is the first Seyfert galaxy in which a strong link between the reddening and intrinsic UV absorption has been found. By comparing our STIS UV and optical spectra with those of the unreddened Seyfert galaxy NGC 4151, we have determined a reddening curve for the nuclear continuum source in NGC 3227 over the 1150-10200 A range. The reddening curve does not show a 2200 A bump and is steeper in the UV than reddening curves derived for the Galaxy, LMC, and SMC, suggesting a preponderance of small dust grains near the nucleus.

http://iopscience.iop.org/article/10.1086/321522/pdf

Absorption and reddening in the seyfert galaxy ngc 3227

We present ASCA results on four prototype powerful far-infrared galaxies, Mrk 231, Mrk 273, Arp 220 and NGC 6240. The soft X-ray spectra show signatures of thermal emission with temperatures of (0.5--1),×107 K, which is probably produced in starbursts. Their soft X-ray (0.5--2 keV) luminosities range from 4×1040 to 7×1041 erg s-1. The X-ray properties are examined in the context of a starburst. Evidence for a heavily obscured active nucleus is found in Mrk 273 and NGC 6240. The ASCA spectra of both galaxies show strong iron K emission-line features. The hard X-ray emission (> 3 keV) in NGC 6240 is most likely the reflected light of a hidden QSO, the intrinsic luminosity of which is suspected to be ∼ 1045 erg s-1, comparable to the far-IR luminosity. The 2--10 keV emission, possibly related to an active galactic nucleus (AGN), is found in Mrk 231. The observed 2--10 keV luminosity is only ∼ 2×1042 erg s-1, and the origin of the hard X-ray emission is uncertain because of the low quality of the present data. No evidence for an AGN is found in Arp 220 in the X-ray data. However, the soft X-ray emission originating in the starburst is also as weak as the Hα nebula and near-IR continuum, despite the large far-IR excess. The possible existence of a powerful but heavily obscured (Compton-thick) AGN is discussed.

/pdf/an-x-ray-investigation-of-powerful-far-infrared-galaxies-dhwlvuctd0.pdf

An X‐ray investigation of powerful far‐infrared galaxies

Optical polarization position angles tend to align with large-scale radio structure in low polarization quasars1, and they tend to align with or be perpendicular to the radio structure in radio galaxies2. In some cases active object emission lines are polarized like the continuum, so the polarization is probably caused by scattering (ref. 3 and R.R.J.A., in preparation). Thus, the polarization alignments indicate the geometrical distribution of scatterers in those cases and so provide information on the matter distribution in the innermost regions. In a new interpretation of the polarization of the Seyfert 2 galaxy NGC1068 (ref. 4), it is noted that the optical polarization of that object is perpendicular to the inner radio contours, while the polarization of the Seyfert 1 galaxy NGC4151 is parallel to the associated radio axis. It is speculated that these are prototypical of two polarization classes of Seyferts analogous to the perpendicular and parallel radio galaxy groups. I show here that this is indeed the case: all Seyfert 1 galaxies in this sample have roughly parallel polarization and all Seyfert 2 galaxies have roughly perpendicular polarizations. These alignment effects can be interpreted as being due to thin and thick scattering disks, respectively, surrounding the continuum sources. This would represent a fundamental difference between the two types of Seyfert galaxies.

Optical polarization position angle versus radio structure axis in Seyfert galaxies

We present new interferometric observations of the 12CO (1¨0), 12CO (2¨1), and HCN (1¨0) molecular line emission in NGC 3227 obtained with the IRAM Plateau de Bure interferometer (PdBI). We achieved an unprecedented angular resolution in the 12CO (2¨1) line of about corresponding to only 0A about 50 pc at a distance of 17.3 Mpc. The mapped 12CO emission is concentrated in the inner 8A and accounts for 20% of the total 30 m 12CO line —ux. The 12CO emission is resolved into an asymmetric nuclear ring with a diameter of about 3A. The HCN line emission is mostly unresolved at our resolution of and contains all of the single-dish —ux. We have decomposed the observed molecular gas D2A.4 motions into a circular and noncircular component revealing that about 80% of the gas in the circumnu- clear region exhibits pure circular rotation. We —nd evidence for bar streaming onto the nuclear ring and a redshifted emission knot on the ring perimeter. In the central arcsecond the gas shows apparent counterrotation. This behavior can be best explained by a warping of the inner molecular gas disk rather than gas motion in a nuclear bar potential. We detected molecular gas at a distance from the nucleus of only D13 pc with a velocity of about 75 km s~1 with respect to the systemic velocity and —nd that within the central arcsecond the rotation curve is rising again. This is the —rst time that millimetric CO line emission has been detected interferometrically at such small distances to the nucleus of a Seyfert galaxy. These measurements indicate a lower limit on the enclosed mass of about 2 ) 107 in the inner 25 pc. M _ Subject headings: galaxies: individual (NGC 3227) ¨ galaxies: ISMgalaxies: nuclei ¨ radio lines: ISM

Distribution and kinematics of the circumnuclear molecular gas in the seyfert 1 galaxy ngc 3227

The observational properties of the ten known AM Her systems are reviewed. A multitude of components of continuum and line radiation from these objects are outlined. We discuss the important physical processes involved in the accretion flow and funnel shock, with emphasis on the properties of the emission line regions. Other topics include the properties of the white dwarf primaries and M dwarf secondaries, the maintenance of synchronous rotation, and the implications of “dumpings” in the known orbital periods (80–115 minutes) and magnetic field strengths (20-35 megagauss).

The AM Herculis Magnetic Variables

The paper presents intermediate resolution observations of the emission line and continuum polarization of the Seyfert galaxies Mrk 3, Mrk 231, NGC 3227, and NGC 3516. The polarization shows a strong wavelength dependence with the polarization increasing smoothly into the blue for each galaxy. This wavelength dependence, together with the presence of polarized H(alpha) emission, indicates that the polarization of each galaxy is caused by an asymmetric dust envelope surrounding the nucleus. Observations of the polarization of the /O III/ lambda 5007 emission in Mrk 3 and NGC 3227, and the polarization through the nonstellar Na ID line absorption in Mrk 231 are used to place constraints on the extent of the polarizing clouds in these galaxies. No polarization variability was detected with time-bases ranging from a few weeks to three years.

/pdf/optical-polarization-of-the-seyfert-galaxies-mrk-3-mrk-231-1uvg5724ja.pdf

Optical polarization of the Seyfert galaxies MRK 3, MRK 231, NGC 3227 and NGC 3516

Measurements of the optical polarizations of the two highly polarized Seyfert 1 galaxies IC 4329A and Mrk 376 are presented. Continuum and line polarization of the two objects were observed with the Steward Observatory 2.25-m telescope using a two-channel photoelectric Pockels cell polarimeter, a single-channel scanner, and a digicon attached to a flint prism spectrograph. Results indicate that, for both galaxies, the emission line polarization and underlying continuum polarization are identical, rising toward short wavelengths, and therefore must be explained by a common mechanism. Such a mechanism is suggested to involve polarization produced by aligned grains in the galactic disk. A model for polarization in IC 4329A by this mechanism predicts a grain size three times smaller than Galactic polarizing grains, as well as a visual extinction of about 2 magnitudes, a gas to dust mass ratio close to 100 and a polarization to extinction ratio comparable to the Galactic ratio.

Optical polarization of the Seyfert galaxies IC 4329A and MRK 376

It is noted that only one BL Lac object, designated 1E 1402.3 + 0416, has so far been discovered as part of an optical identification program for a complete sample of faint X-ray sources detected with the Einstein Observatory. Consistent with previously X-ray-discovered BL Lacs, this object is blue and radio weak (17 mJy at 6 cm). It is pointed out that the percentage of BL Lacs in the faint extragalactic X-ray sample (2%) is smaller than the percentage at higher X-ray fluxes (6%). Over the same range in X-ray flux, the percentage of emission-line active galaxy nuclei (QSO + Seyferts) rises from 40% to 74%). This is seen as suggesting that BL Lacs do not evolve in a manner similar to quasars and are, therefore, not substantial contributors to the X-ray background.

/pdf/discovery-of-a-new-bl-lacertae-object-1e-1402-3-0416-with-4n0jo8aavi.pdf

Discovery of a new BL Lacertae object /1E 1402.3 + 0416/ with the Einstein Observatory

In 1981 Steward Observatory developed and put into use an intensified photon-counting Reticon detector system for the Cassegrain spectrograph on the observatory's 2.3 meter telescope. During initial design of the detector, particular emphasis was placed on selecting image intensifier components that would provide the highest possible quantum efficiency in the blue spectral region as well as provide a superior pulse-height distribution, good uniformity of response, high resolution from center to edge, and excellent geometrical stability. The Reticon camera electronics and discriminator electronics are the products of a cooperative project between Steward Observatory and the Smithsonian Astrophysical Observatory, and represent a newer technology version of the design pioneered by Shectman and Hiltner. The paper presents a description of the detector components, a summary of laboratory evaluation tests, and a summary of the detector's performance at the telescope. Of special significance is a discussion of the detector's true counting efficiency.

H. S. Stockman

Papers

The AM Herculis Magnetic Variables

Optical polarization of the Seyfert galaxies MRK 3, MRK 231, NGC 3227 and NGC 3516

Optical polarization of the Seyfert galaxies IC 4329A and MRK 376

Discovery of a new BL Lacertae object /1E 1402.3 + 0416/ with the Einstein Observatory

The Steward Observatory Intensified Photon-Counting Reticon System