21,360 research outputs found
Interferometric CO observations of the ultraluminous IRAS galaxies ARP 220, IC 694/NGC 3690, NGC 6420 and NGC 7469
High resolution CO observations of the IRAS galaxies Arp 220, IC 694/NGC 3690, NGC 6240 and NGC 7469 were made with the Millimeter Wave Interferometer of the Owen Valley Radio Observatory. These yield spatial information on scales of 1 to 5 kpc and allow the separation of compact condensations from the more extended emission in the galaxies. In the case of the obviously interacting system IC 694/NGC 3690 the contributions of each component can be discerned. For that galaxy, and also for Arp 220, the unusually high lumonisities may be produced by nonthermal processes rather than by intense bursts of star formation
The IRAS Revised Bright Galaxy Sample (RBGS)
IRAS flux densities, redshifts, and infrared luminosities are reported for
all sources identified in the IRAS Revised Bright Galaxy Sample (RBGS), a
complete flux-limited survey of all extragalactic objects with total 60 micron
flux density greater than 5.24 Jy, covering the entire sky surveyed by IRAS at
Galactic latitude |b| > 5 degrees. The RBGS includes 629 objects, with a median
(mean) sample redshift of 0.0082 (0.0126) and a maximum redshift of 0.0876. The
RBGS supersedes the previous two-part IRAS Bright Galaxy Samples, which were
compiled before the final ("Pass 3") calibration of the IRAS Level 1 Archive in
May 1990. The RBGS also makes use of more accurate and consistent automated
methods to measure the flux of objects with extended emission. Basic properties
of the RBGS sources are summarized, including estimated total infrared
luminosities, as well as updates to cross-identifications with sources from
optical galaxy catalogs established using the NASA/IPAC Extragalactic Database
(NED). In addition, an atlas of images from the Digitized Sky Survey with
overlays of the IRAS position uncertainty ellipse and annotated scale bars is
provided for ease in visualizing the optical morphology in context with the
angular and metric size of each object. The revised bolometric infrared
luminosity function, phi(L_ir), for infrared bright galaxies in the local
Universe remains best fit by a double power law, phi(L_ir) ~ L_ir^alpha, with
alpha = -0.6 (+/- 0.1), and alpha = -2.2 (+/- 0.1) below and above the
"characteristic" infrared luminosity L_ir ~ 10^{10.5} L_solar, respectively.
(Abridged)Comment: Accepted for publication in the Astronomical Journal. Contains 50
pages, 7 tables, 16 figures. Due to astro-ph space limits, only 1 of 26 pages
of Figure 1, and 1 of 11 pages of Table 7, are included; full resolution
Postscript files are available at
http://nedwww.ipac.caltech.edu/level5/March03/IRAS_RBGS/Figures/ .
Replacement: Corrected insertion of Fig. 15 (MethodCodes.ps) in LaTe
Submilliamp threshold InGaAs-GaAs strained layer quantum-well laser
Strained-layer InGaAs-GaAs single-quantum-well buried-heterostructure lasers were fabricated by a hybrid beam epitaxy and liquid-phase epitaxy technique. Very low threshold currents, 2.4 mA for an uncoated laser (L=425 μm) and 0.75 mA for a coated laser (R~0.9, L=198 μm), were obtained. A 3-dB modulation bandwidth of 7.6 GHz was demonstrated at low bias current (14 mA). Procedures for material preparation and device fabrication are introduced
Optical Spectroscopy of the IRAS 1-Jy Sample of Ultraluminous Infrared Galaxies
This paper discusses the optical spectroscopic properties of the IRAS 1-Jy
sample of ultraluminous infrared galaxies (ULIGs). One hundred and eight of the
118 1-Jy ULIGs have been observed at dlambda = 8.3 AA resolution over the
wavelength range ~4500 A -- 8900 A. These data are combined with large,
previously published sets of optical spectroscopic data of lower luminosity
infrared galaxies to look for systematic trends with infrared luminosity over
the luminosity range L_ir ~ 10^{10.5}-10^{13} L_sun. As found in previous
studies, the fraction of Seyfert galaxies among luminous infrared galaxies
increases abruptly above L_ir ~ 10^{12.3} L_sun --- about 50% of the galaxies
with L_ir > 10^{12.3} L_sun present Seyfert characteristics. Many of the
optical and infrared spectroscopic properties of the Seyfert galaxies are
consistent with the presence of a genuine active galactic nucleus (AGN). About
30% of these galaxies are Seyfert 1s with broad-line regions similar to those
of optical quasars. The percentage of Seyfert 1 ULIGs increases with infrared
luminosity, contrary to the predictions of the standard unification model for
Seyfert galaxies. Comparisons of the broad-line luminosities of optical and
obscured Seyfert 1 ULIGs with those of optically selected quasars of comparable
bolometric luminosity suggest that the dominant energy source in most of these
ULIGs is the same as in optical quasars, namely mass accretion onto a
supermassive black hole, rather than a starburst. These results are consistent
with recently published ISO, ASCA, and VLBI data. (abridged)Comment: Text and 23 figures (45 pages), Tables 1 - 6 (16 pages
Molecular Gas and Nuclear Activity in Radio Galaxies Detected by IRAS
This paper reports the latest results from a millimeter-wave (CO)
spectroscopic survey of IRAS-detected radio galaxies with L_1.4GHz ~ 10^23-28
W/Hz in the redshift range z ~ 0.02-0.15. The IRAS flux-limited sample contains
33 radio galaxies with different radio morphologies and a broad range of
infrared luminosities L_IR = 10^9-12 L_sun), allowing for an investigation of
(a) whether low-z radio-selected AGN reside in molecular gas-rich host galaxes,
and (b) whether the CO properties are correlated with the properties of the
host galaxy or the AGN. All of the radio galaxies in Mazzarella et al. (1993)
and Mirabel et al. (1989) have been reobserved. Three new CO detections have
been made, raising the total number of CO detections to nine and setting the
survey detection rate at ~ 25%. Many of the CO lines have double-peaked
profiles, and the CO line widths are broad (average Delta v_FWHM ~ 500+/-130
km/s), exceeding the average CO widths of both ultraluminous infrared galaxies
(300+/-90 km/s) and Palomar-Green QSOs (260+/-160 km/s), and thus being
indicative of massive host galaxies. The CO luminosities translate into
molecular gas masses of ~ 0.4-7x10^9 M_sun, however, the 3-sigma CO upper
limits for nondetections do not rule out a molecular gas mass as high as that
of the Milky Way (~ 3x10^9 M_sun). Optical images of eight out of nine
molecular gas-rich radio galaxies show evidence of close companions and/or
tidal features. Finally, there is no obvious correlation between radio power
and molecular gas mass. However, it is notable that only one F-R II galaxy out
of 12 is detected in this CO survey; the remaining detections are of galaxies
hosting F-R I and compact radio jets.Comment: LaTex, 33 pages, including 1 jpg figure and 14 postscript figures,
ApJS, in press (August 2005
Reaction Time of a Group of Physics Students
The reaction time of a group of students majoring in Physics is reported
here. Strong co-relation between fatigue, reaction time and performance have
been seen and may be useful for academicians and administrators responsible of
working out time-tables, course structures, students counsellings etc.Comment: 10 pages, 4 figure
Quantum walks in higher dimensions
We analyze the quantum walk in higher spatial dimensions and compare
classical and quantum spreading as a function of time. Tensor products of
Hadamard transformations and the discrete Fourier transform arise as natural
extensions of the quantum coin toss in the one-dimensional walk simulation, and
other illustrative transformations are also investigated. We find that
entanglement between the dimensions serves to reduce the rate of spread of the
quantum walk. The classical limit is obtained by introducing a random phase
variable.Comment: 6 pages, 6 figures, published versio
Acute effects of dietary fat composition on postprandial plasma bile acid and cholecystokinin concentrations in healthy premenopausal women
Optical/Near-Infrared Imaging of Infrared-Excess Palomar-Green QSOs
Ground-based high spatial-resolution (FWHM < 0.3-0.8") optical and
near-infrared imaging (0.4-2.2um) is presented for a complete sample of
optically selected Palomar-Green QSOs with far-infrared excesses at least as
great as those of "warm" AGN-like ultraluminous infrared galaxies
(L_ir/L_big-blue-bump > 0.46). In all cases, the host galaxies of the QSOs were
detected and most have discernable two-dimensional structure. The QSO host
galaxies and the QSO nuclei are similar in magnitude at H-band. H-band
luminosities of the hosts range from 0.5-7.5 L* with a mean of 2.3 L*, and are
consistent with those found in ULIGs. Both the QSO nuclei and the host galaxies
have near-infrared excesses, which may be the result of dust associated with
the nucleus and of recent dusty star formation in the host. These results
suggest that some, but not all, optically-selected QSOs may have evolved from
an infrared-active state triggered by the merger of two similarly-sized L*
galaxies, in a manner similar to that of the ultraluminous infrared galaxies.Comment: Aastex format, 38 pages, 4 tables, 10 figures. Higher quality figures
are available in JPG forma
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