2,385 research outputs found
The Optical Polarization Properties of X-ray Selected BL Lacertae Objects
We discuss the optical polarization properties of X-ray selected BL Lacertae
objects (XSBLs) as determined from three years of monitoring 37 BL Lac objects
and candidates. The observed objects include a complete X-ray flux limited
sample drawn from the EMS Survey. The majority of the XSBLs classi- fied solely
on the appearance of their spectra are members of the class of BL~Lacs since
they possess intrinsically polarized and variable continua. The duty cycle of
polarized emission from XSBLs is 40\%. The majority of XSBLs (\%)
have preferred polarization position angles on time scales as long as three
years. This reflects stability in the geometry of the region emitting the
polarized optical emission. We discuss the observed spectral dependence of the
degree of polarization and some of the possible mechanisms for producing the
observed characteristics. While dilution of the polarized emission by the host
galaxy starlight is present in some objects, we demon- strate that the average
polarization properties derived from our observations are not drastically
affected by this effect. The objects in our monitored sample did not display
the larger than one magnitude variations generally used to characterize the
optical variability of blazars in general.Comment: LaTex file, 21 pages, with tables appended as a poscript file.
Contact [email protected] for postscript figure files. Institute for Advanced
Study number AST 93/4
Finance, Control, and Profitability: The Influence of German Banks
Bank intermediated finance has been cited frequently as the preferred means for channeling funds from savers to firms. Germany is the prototypical economy where universal banks allegedly exert substantial influence over firms. Despite frequent assertions about the considerable power of German banks and the advantages of a bank relation, empirical support is mixed. With a unique dataset and a focus on the fragility/sturdiness of inferences, this paper evaluates German bank influence in terms of three hypotheses: 1) do bank influenced firms enjoy lower finance costs? [No]; 2) is bank influence a solution to control problems? [Yes]; 3) do bank influenced firms have higher profitability? [No]. Coupled with results about the control consequences of concentrated ownership, these results suggest that bank influence serves as a substitute control mechanism, one of several available for addressing corporate control problems.German banks, corporate finance and governance
The Hidden Nuclear Spectrum of the Luminous IRAS Source FSC102144724
Optical spectropolarimetry of the luminous IRAS source FSC102144724
(z) reveals that the strong (\twid17\%) linear polarization detected by
Lawrence \etal\/ is shared by both the narrow UV emission lines and the
underlying continuum. This observation and the brightness of the source rule
out synchrotron emission and dichroic extinction by dust as the polarizing
mechanism, leaving scattering as the only plausible cause of the polarized
emission. The narrowness of the lines requires that the scatterers be dust
grains or cool (10~K) electrons. We can recover the spectrum
that is incident on the scattering medium provided we make some reasonable
assumptions regarding the source geometry. The scattered UV spectrum has a
power law index ~ of (), steeper
than what would be expected from a young burst of star formation, but similar
to many AGN.Comment: 10 pages, with figure, uuencoded postscript Institute for Advanced
Study number AST 94/1
An IR-Selected Galaxy Cluster at z=1.27
We report the discovery of a galaxy cluster at z=1.27. ClG J0848+4453 was
found in a near-IR field survey as a high density region of objects with very
red J-K colors. Optical spectroscopy of a limited number of 24 < R < 25 objects
in the area shows that 6 galaxies within a 90 arcsec (0.49/h Mpc, q_O = 0.1)
diameter region lie at z=1.273 +/- 0.002. Most of these 6 member galaxies have
broad-band colors consistent with the expected spectral energy distribution of
a passively-evolving elliptical galaxy formed at high redshift. An additional 2
galaxies located ~2 arcmin from the cluster center are also at z=1.27. Using
all 8 of these spectroscopic members, we estimate the velocity dispersion is
700 +/- 180 km/s, similar to that of Abell R=1 clusters in the present epoch. A
deep Rosat PSPC observation detects X-ray emission at the 5 sigma level
coincident with the nominal cluster center. Assuming that the X-ray flux is
emitted by hot gas trapped in the potential well of a collapsed system (no AGN
is known to exist in the area), the resulting X-ray luminosity in the rest
frame 0.1-2.4 keV band of L_x = 1.5 x 10^44 ergs/s suggests the presence of a
moderately large mass. ClG J0848+4453 is the highest redshift cluster found
without targetting a central active galaxy.Comment: Accepted for publication in The Astronomical Journal; 22 pages, 6
figures; corrected titl
drĂĄma 4 felvonĂĄsban - Ărta EugĂ©ne Brieux - fordĂtotta ZigĂĄny ĂrpĂĄd - rendezĆ KemĂ©ny Lajos
VĂĄrosi SzinhĂĄz. Debreczen, 1913 februĂĄr 15 -Ă©n szombaton: K. Hegyesy Mari Ă©s Beregi OszkĂĄr a budapesti nemzeti szinhĂĄz mƱvĂ©szeinek egyĂŒttes fellĂ©ptĂ©vel.Debreceni Egyetem Egyetemi Ă©s Nemzeti KönyvtĂĄ
Distant radio galaxies in the near IR
We are carrying out a program of near IR imaging and spectroscopy of radio galaxies with redshifts of 1.5 and greater. One of its principal goals is to constrain the ages and star formation histories of massive galaxies at early epochs. The radio galaxies are drawn from the survey of 1Jy class sources by McCarthy et al (1989) and McCarthy (1990). The sample contains 18 radio galaxies with redshifts greater than 2 and an additional 10 objects with 1.5 less than z less than 2.0. The redshifts were obtained from long slit spectra with the CTIO 4 m. While the galaxies are quite faint (r approximately = 21-24.5) all have Lyman alpha emission with rest frame equivalent widths of 100 - 1000 A. Multicolor photometry in the g,r,i and J,H,K bands has been obtained with the 2.5-m Du Pont Telescope on Las Campanas and with the Hale 5 m telescope at Palomar. We have recently obtained near IR spectra, using the 4 m telescopes at KPNO and CTIO, of a few objects with the goal of determining the Lyman alpha/H-alpha ratio and hence the reddening
Probing the Super Star Cluster Environment of NGC 1569 Using FISICA
We present near-IR JH spectra of the central regions of the dwarf starburst
galaxy NGC 1569 using the Florida Image Slicer for Infrared Cosmology and
Astrophysics (FISICA). The dust-penetrating properties and available spectral
features of the near-IR, combined with the integral field unit (IFU) capability
to take spectra of a field, make FISICA an ideal tool for this work. We use the
prominent [He I] (1.083\mu m) and Pa\beta (1.282 \mu m) lines to probe the
dense star forming regions as well as characterize the general star forming
environment around the super star clusters (SSCs) in NGC 1569. We find [He I]
coincident with CO clouds to the north and west of the SSCs, which provides the
first, conclusive evidence for embedded star clusters here.Comment: 6 pages, 3 figures, accepted for publication in the MNRA
Zenithal bistability in a nematic liquid crystal device with a monostable surface condition
The ground-state director configurations in a grating-aligned, zenithally bistable nematic device are calculated in two dimensions using a Q tensor approach. The director profiles generated are well described by a one-dimensional variation of the director across the width of the device, with the distorted region near the grating replaced by an effective surface anchoring energy. This work shows that device bistability can in fact be achieved by using a monostable surface term in the one-dimensional model. This implies that is should be possible to construct a device showing zenithal bistability without the need for a micropatterned surface
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