5,871 research outputs found
Theophilus North
I was born an identical twin, and the twin only lived a few hours, but he would have been called Theophilus; so, this is my other self. The framework is the same as mine, but he\u27s a very different fellow from me; so, it\u27s how my life might have been had I been born that other fellow. It\u27s first autobiography and then fiction, but I don\u27t know of any other work where the author was imagining himself as his anti-self. I\u27m dutiful, Iâm conscientious, Iâm school masterish, but Theophilus is a helluva fella. A liar but a very good man--and I\u27m not as altruistic as he is--he\u27s that mixture of the scoundrel in the frustrated saint. (Theophilus North is) a comedy with very seldom underground. -Thornton Wilder in The Guardian. The approach to the development of Thornton Wilder\u27s novel Theophilus North into a Chamber Theatre script is based on the author\u27s own conception cited above. The intent of the script is to show that Ted North is, indeed âa helluva fella.
HST Imaging Polarimetry of the Gravitational Lens FSC10214+4724
We present imaging polarimetry of the extremely luminous, redshift 2.3 IRAS
source FSC10214+4724. The observations were obtained with HST's Faint Object
Camera in the F437M filter, which is free of strong emission lines. The 0.7
arcsec long arc is unresolved to 0.04 arcsec FWHM in the transverse direction,
and has an integrated polarization of 28 +/- 3 percent, in good agreement with
ground-based observations. The polarization position angle varies along the arc
by up to 35 deg. The overall position angle is 62 +/- 3 deg east of north. No
counterimage is detected to B = 27.5 mag (), giving an observed arc to
counterimage flux ratio greater than 250, considerably greater than the flux
ratio of 100 measured previously in the I-band. This implies that the
configuration of the object in the source plane at the B-band is different from
that at I-band, and/or that the lensing galaxy is dusty.Comment: 17 pages, 3 figures. Accepted for publication in Astronomical
Journal, February 199
Heavy X-ray obscuration in the most-luminous galaxies discovered by WISE
Hot Dust-Obscured Galaxies (Hot DOGs) are hyperluminous
() infrared galaxies with
extremely high (up to hundreds of K) dust temperatures. The sources powering
both their extremely high luminosities and dust temperatures are thought to be
deeply buried and rapidly accreting supermassive black holes (SMBHs). Hot DOGs
could therefore represent a key evolutionary phase in which the SMBH growth
peaks. X-ray observations can be used to study their obscuration levels and
luminosities. In this work, we present the X-ray properties of the 20
most-luminous () known Hot DOGs at
. Five of them are covered by long-exposure ( ks) Chandra and
XMM-Newton observations, with three being X-ray detected, and we study their
individual properties. One of these sources (W01160505) is a Compton-thick
candidate, with column density
derived from X-ray spectral fitting. The remaining 15 Hot DOGs have been
targeted by a Chandra snapshot (3.1 ks) survey. None of these 15 is
individually detected; therefore we applied a stacking analysis to investigate
their average emission. From hardness-ratio analysis, we constrained the
average obscuring column density and intrinsic luminosity to be
log and
, which are consistent with
results for individually detected sources. We also investigated the
and relations, finding hints that Hot
DOGs are typically X-ray weaker than expected, although larger samples of
luminous obscured QSOs are needed to derive solid conclusions.Comment: MNRAS, accepted 2017 November 29 . Received 2017 November 29 ; in
original form 2017 October 11. 15 pages, 6 figure
Hubble Space Telescope Observations of the Luminous IRAS Source FSC 10214+4724: A Gravitationally Lensed Infrared Quasar
With a redshift of 2.3, the IRAS source FSC 10214+4724 is apparently one of the most luminous objects known in the universe. We present an image of FSC 10214+4724 at 0.8 pm obtained with the Hubble Space Telescope (HST) WFPC2 Planetary Camera. The source appears as an unresolved (less then 0.06) arc 0.7 long, with significant substructure along its length. The center of curvature of the arc is located near an elliptical galaxy 1.18 to the north. An unresolved component 100 times fainter than the arc is clearly detected on the opposite side of this galaxy. The most straightforward interpretation is that FSC 10214+4724 is gravitationally lensed by the foreground elliptical galaxy, with the faint component a counter-image of the IRAS source. The brightness of the arc in the HST image is then magnified by approx. 100, and the intrinsic source diameter is approx. 0.0l (80 pc) at 0.25 microns rest wavelength. The bolometric luminosity is probably amplified by a smaller factor (approx. 30) as a result of the larger extent expected for the source in the far-infrared. A detailed lensing model is presented that reproduces the observed morphology and relative flux of the arc and counterimage and correctly predicts the position angle of the lensing galaxy. The model also predicts reasonable values for the velocity dispersion, mass, and mass-to-light ratio of the lensing galaxy for a wide range of galaxy redshifts. A redshift for the lensing galaxy of -0.9 is consistent with the measured surface brightness profile from the image, as well as with the galaxy's spectral energy distribution. The background lensed source has an intrinsic luminosity approx. 2 x 10(exp 13) L(solar mass) and remains a highly luminous quasar with an extremely large ratio of infrared to optical/ultraviolet luminosity
Controlling Effect of Geometrically Defined Local Structural Changes on Chaotic Hamiltonian Systems
An effective characterization of chaotic conservative Hamiltonian systems in
terms of the curvature associated with a Riemannian metric tensor derived from
the structure of the Hamiltonian has been extended to a wide class of potential
models of standard form through definition of a conformal metric. The geodesic
equations reproduce the Hamilton equations of the original potential model
through an inverse map in the tangent space. The second covariant derivative of
the geodesic deviation in this space generates a dynamical curvature, resulting
in (energy dependent) criteria for unstable behavior different from the usual
Lyapunov criteria. We show here that this criterion can be constructively used
to modify locally the potential of a chaotic Hamiltonian model in such a way
that stable motion is achieved. Since our criterion for instability is local in
coordinate space, these results provide a new and minimal method for achieving
control of a chaotic system
Submillimetre observations of WISE-selected high-redshift, luminous, dusty galaxies
We present SCUBA-2 850um submillimetre (submm) observations of the fields of
10 dusty, luminous galaxies at z ~ 1.7 - 4.6, detected at 12um and/or 22um by
the WISE all-sky survey, but faint or undetected at 3.4um and 4.6um; dubbed
hot, dust-obscured galaxies (Hot DOGs). The six detected targets all have total
infrared luminosities greater than 10^13 L_sun, with one greater than 10^14
L_sun. Their spectral energy distributions (SEDs) are very blue from
mid-infrared to submm wavelengths and not well fitted by standard AGN SED
templates, without adding extra dust extinction to fit the WISE 3.4um and 4.6um
data. The SCUBA-2 850um observations confirm that the Hot DOGs have less cold
and/or more warm dust emission than standard AGN templates, and limit an
underlying extended spiral or ULIRG-type galaxy to contribute less than about
2% or 55% of the typical total Hot DOG IR luminosity, respectively. The two
most distant and luminous targets have similar observed submm to mid-infrared
ratios to the rest, and thus appear to have even hotter SEDs. The number of
serendipitous submm galaxies (SMGs) detected in the 1.5-arcmin-radius SCUBA-2
850um maps indicates there is a significant over-density of serendipitous
sources around Hot DOGs. These submm observations confirm that the
WISE-selected ultra-luminous galaxies have very blue mid-infrared to submm
SEDs, suggesting that they contain very powerful AGN, and are apparently
located in unusual arcmin-scale overdensities of very luminous dusty galaxies.Comment: 12 pages, 8 figures, 3 tables, accepted for publication in MNRA
Evolution of the UV Excess in Early-Type Galaxies
We examine the UV emission from luminous early-type galaxies as a function of
redshift. We perform a stacking analysis using Galaxy Evolution Explorer
(GALEX) images of galaxies in the NOAO Deep Wide Field Survey (NDWFS) Bo\"otes
field and examine the evolution in the UV colors of the average galaxy. Our
sample, selected to have minimal ongoing star formation based on the optical to
mid-IR SEDs of the galaxies, includes 1843 galaxies spanning the redshift range
. We find evidence that the strength of the UV excess
decreases, on average, with redshift, and our measurements also show moderate
disagreement with previous models of the UV excess. Our results show little
evolution in the shape of the UV continuum with redshift, consistent either
with the binary model for the formation of Extreme Horizontal Branch (EHB)
stars or with no evolution in EHB morphology with look-back time. However, the
binary formation model predicts that the strength of the UV excess should also
be relatively constant, in contradiction with our measured results. Finally, we
see no significant influence of a galaxy's environment on the strength of its
UV excess.Comment: 30 pages, 10 figures; accepted by ApJ. Modified from original version
to reflect referee's comment
The Galaxy Population of Cluster RXJ0848+4453 at z=1.27
We present a study of the galaxy population in the cluster RXJ0848+4453 at
z=1.27, using deep HST NICMOS and WFPC2 images. We morphologically classify all
galaxies to K_s=20.6 that are covered by the HST imaging, and determine
photometric redshifts using deep ground based BRIzJK_s photometry. Of 22 likely
cluster members with morphological classifications, eleven (50%) are classified
as early-type galaxies, nine (41%) as spiral galaxies, and two (9%) as
``merger/peculiar''. At HST resolution the second brightest cluster galaxy is
resolved into a spectacular merger between three red galaxies of similar
luminosity, separated from each other by ~6 kpc, with an integrated magnitude
K=17.6 (~3 L* at z=1.27). The two most luminous early-type galaxies also show
evidence for recent or ongoing interactions. Mergers and interactions between
galaxies are possible because RXJ0848+4453 is not yet relaxed. The fraction of
early-type galaxies in our sample is similar to that in clusters at 0.5<z<1,
and consistent with a gradual decrease of the number of early-type galaxies in
clusters from z=0 to z=1.3. We find evidence that the color-magnitude relation
of the early-type galaxies is less steep than in the nearby Coma cluster. This
may indicate that the brightest early-type galaxies have young stellar
populations at z=1.27, but is also consistent with predictions of single age
``monolithic'' models with a galactic wind. The scatter in the color-magnitude
relation is ~0.04 in rest frame U-V, similar to that in clusters at 0<z<1.
Taken together, these results show that luminous early-type galaxies exist in
clusters at z~1.3, but that their number density may be smaller than in the
local Universe. Additional observations are needed to determine whether the
brightest early-type galaxies harbor young stellar populations.Comment: Accepted for publication in The Astrophysical Journal Letter
Characterizing the Mid-IR Extragalactic Sky with WISE and SDSS
The Wide-field Infrared Survey Explorer (WISE) has completed its all-sky
survey at 3.4-22 micron. We merge the WISE data with optical SDSS data and
provide a phenomenological characterization of mid-IR, extragalactic sources.
WISE is most sensitive at 3.4micron(W1) and least at 22micron(W4). The W1 band
probes massive early-type galaxies out to z\gtrsim1. This is more distant than
SDSS identified early-type galaxies, consistent with the fact that 28% of
3.4micron sources have faint or no r-band counterparts (r>22.2). In contrast,
92-95% of 12 and 22micron sources have SDSS optical counterparts with r<22.2.
WISE 3.4micron detects 89.8% of the entire SDSS QSO catalog at SNR(W1)>7, but
only 18.9% at 22micron with SNR(W4)>5. We show that WISE colors alone are
effective in isolating stars (or local early-type galaxies), star-forming
galaxies and strong AGN/QSOs at z<3. We highlight three major applications of
WISE colors: (1) Selection of strong AGN/QSOs at z0.8 and
W2<15.2 criteria, producing a census of this population. The surface density of
these strong AGN/QSO candidates is 67.5+-0.14/deg^2. (2) Selection of
dust-obscured, type-2 AGN/QSO candidates. We show that WISE W1-W2>0.8, W2<15.2
combined with r-W2>6 (Vega) colors can be used to identify type-2 AGN
candidates. The fraction of these type-2 AGN candidates is 1/3rd of all WISE
color-selected AGNs. (3) Selection of ULIRGs at z\sim2 with extremely red
colors, r-W4>14 or well-detected 22micron sources lacking detections in the 3.4
and 4.6micron bands. The surface density of z~2 r-W4>14 ULIRGs is
0.9+-0.07/deg^2 at SNR(W4)>5 (flux(W4)>=2.5mJy), which is consistent with that
inferred from smaller area Spitzer surveys. Optical spectroscopy of a small
number of these high-redshift ULIRGs confirms our selection, and reveals a
possible trend that optically fainter or r-W4 redder candidates are at higher
redshifts.Comment: 41 pages, 20 figures, Accepted for publication by the Astronomical
Journa
The Evolution of Early-Type Galaxies in Distant Clusters
We present results from an optical-IR photometric study of early-type
galaxies in 19 galaxy clusters out to z=0.9. The galaxy sample is selected on
the basis of morphologies determined from HST WFPC2 images, and is
photometrically defined in the K-band to minimize redshift-dependent selection
biases. The optical-IR colors of the early-type cluster galaxies become bluer
with increasing redshift in a manner consistent with the passive evolution of
an old stellar population formed at an early cosmic epoch. The degree of color
evolution is similar for clusters at similar redshift, and does not depend
strongly on the optical richness or X-ray luminosity of the cluster, suggesting
that the history of early-type galaxies is relatively insensitive to
environment. The slope of the color-magnitude relationship shows no significant
change out to z=0.9, providing evidence that it arises from a correlation
between galaxy mass and metallicity, not age. Finally, the intrinsic scatter in
the optical-IR colors is small and nearly constant with redshift, indicating
that the majority of giant, early-type galaxies in clusters share a common star
formation history, with little perturbation due to uncorrelated episodes of
later star formation. Taken together, our results are consistent with models in
which most early-type galaxies in rich clusters are old, formed the majority of
their stars at high redshift in a well-synchronized fashion, and evolved
quiescently thereafter.Comment: 55 pages, 24 figures, uses AASTeX. Accepted for publication in The
Astrophysical Journa
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