136 research outputs found
Everything comes full circle
Following Wim Wenders’ Paris, Texas (1984) filming locations from Houston, Texas to Los Angeles, California, I use a 16mm Bolex camera to capture the vastness of the American West. The footage draws me to reminisce about snippets of my everyday life. I contemplate how we perceive the world through analog optical apparatuses and how memories are multidimensional yet fragile. Our recollections of people and places can be distorted, unrecognizable, and fictitious. These memories would eventually diminish with the passing of time. By converting the filmmaking back and forth between analog and digital filmmaking, with the loss of information during the process of recording and recreating, Everything Comes Full Circle is my attempt to remember things that will soon be forgotten
Swift Monitoring Observations of Mrk 231: Detection of Ultraviolet Variability
We analyze 168 Swift monitoring observations of the nearest broad absorption
line quasar Mrk 231 in the UV and X-ray bands, where we detect significant
variability in the UV (2246\AA) light curve with a null probability of
for a constant model. Separately, from an archival sample
of Swift observed active galactic nuclei (AGN), we measure the relation between
UV excess variance and luminosity, finding that the normalized UV excess
variance decreases with luminosity. Comparing to this mean relation, the
normalized UV excess variance of Mrk 231 is smaller, however within the scatter
characterising the full population. The upper limit of the X-ray excess
variance is consistent with other AGN. The power spectrum density of the UV
light curve can be well fit by a power law model with a slope of
between and Hz, consistent with those for typical AGN,
with no obvious quasi-periodical oscillation peaks. The UV variability and its
power spectrum suggest that a significant amount of the UV emission of Mrk 231
is from the accretion disk. The consistencies in the normalized UV variability
and the shape of the power spectrum density between Mrk 231 and other normal
AGN suggest that the origin of UV variability of broad absorption line quasars
is similar to other AGN, and dust scattering at large scales such as the torus
is not a dominating process for the UV emission of Mrk 231. Significant
scattering, if present, is constrained to smaller than 10 light days. We
perform lagged correlation analysis between the UV and X-ray light curves and
find the correlation insignificant within the present data.Comment: 8 pages, 4 figures, accepted by MNRA
Identifying Strongly Lensed Gravitational Waves with the Third-generation Detectors
The joint detection of GW signals by a network of instruments will increase
the detecting ability of faint and far GW signals with higher signal-to-noise
ratios (SNRs), which could improve the ability of detecting the lensed GWs as
well, especially for the 3rd generation detectors, e.g. Einstein Telescope (ET)
and Cosmic Explorer (CE). However, identifying Strongly Lensed Gravitational
Waves (SLGWs) is still challenging. We focus on the identification ability of
3G detectors in this article. We predict and analyze the SNR distribution of
SLGW signals and prove only 50.6\% of SLGW pairs detected by ET alone can be
identified by Lens Bayes factor (LBF), which is a popular method at present to
identify SLGWs. For SLGW pairs detected by CE\&ET network, owing to the
superior spatial resolution, this number rises to 87.3\%. Moreover, we get an
approximate analytical relation between SNR and LBF. We give clear SNR limits
to identify SLGWs and estimate the expected yearly detection rates of
galaxy-scale lensed GWs that can get identified with 3G detector network.Comment: 9 pages, 7 figure
A rest-frame near-IR study of clumps in galaxies at 1 < z < 2 using JWST/NIRCam: connection to galaxy bulges
A key question in galaxy evolution has been the importance of the apparent
`clumpiness' of high redshift galaxies. Until now, this property has been
primarily investigated in rest-frame UV, limiting our understanding of their
relevance. Are they short-lived or are associated with more long-lived massive
structures that are part of the underlying stellar disks? We use JWST/NIRCam
imaging from CEERS to explore the connection between the presence of these
`clumps' in a galaxy and its overall stellar morphology, in a mass-complete
() sample of galaxies at .
Exploiting the uninterrupted access to rest-frame optical and near-IR light, we
simultaneously map the clumps in galactic disks across our wavelength coverage,
along with measuring the distribution of stars among their bulges and disks.
Firstly, we find that the clumps are not limited to rest-frame UV and optical,
but are also apparent in near-IR with spatial overlap. This
rest-frame near-IR detection indicates that clumps would also feature in the
stellar-mass distribution of the galaxy. A secondary consequence is that these
will hence be expected to increase the dynamical friction within galactic disks
leading to gas inflow. We find a strong negative correlation between how clumpy
a galaxy is and strength of the bulge. This firmly suggests an evolutionary
connection, either through clumps driving bulge growth, or the bulge
stabilizing the galaxy against clump formation, or a combination of the two.
Finally, we find evidence of this correlation differing from rest-frame optical
to near-IR, which could suggest a combination of varying formation modes for
the clumps.Comment: Accepted for publication in Ap
Melatonin, a Full Service Anti-Cancer Agent: Inhibition of Initiation, Progression and Metastasis
There is highly credible evidence that melatonin mitigates cancer at the initiation, progression and metastasis phases. In many cases, the molecular mechanisms underpinning these inhibitory actions have been proposed. What is rather perplexing, however, is the large number of processes by which melatonin reportedly restrains cancer development and growth. These diverse actions suggest that what is being observed are merely epiphenomena of an underlying more fundamental action of melatonin that remains to be disclosed. Some of the arresting actions of melatonin on cancer are clearly membrane receptor-mediated while others are membrane receptor-independent and involve direct intracellular actions of this ubiquitously-distributed molecule. While the emphasis of melatonin/cancer research has been on the role of the indoleamine in restraining breast cancer, this is changing quickly with many cancer types having been shown to be susceptible to inhibition by melatonin. There are several facets of this research which could have immediate applications at the clinical level. Many studies have shown that melatonin’s co-administration improves the sensitivity of cancers to inhibition by conventional drugs. Even more important are the findings that melatonin renders cancers previously totally resistant to treatment sensitive to these same therapies. Melatonin also inhibits molecular processes associated with metastasis by limiting the entrance of cancer cells into the vascular system and preventing them from establishing secondary growths at distant sites. This is of particular importance since cancer metastasis often significantly contributes to death of the patient. Another area that deserves additional consideration is related to the capacity of melatonin in reducing the toxic consequences of anti-cancer drugs while increasing their efficacy. Although this information has been available for more than a decade, it has not been adequately exploited at the clinical level. Even if the only beneficial actions of melatonin in cancer patients are its ability to attenuate acute and long-term drug toxicity, melatonin should be used to improve the physical wellbeing of the patients. The experimental findings, however, suggest that the advantages of using melatonin as a co-treatment with conventional cancer therapies would far exceed improvements in the wellbeing of the patients.Shun-Fa Yang, Grant #CHS-2016-E-002-Y2
Early Results from GLASS-JWST. VIII. An Extremely Magnified Blue Supergiant Star at Redshift 2.65 in the A2744 Cluster Field
We report the discovery of an extremely magnified star at redshift z = 2.65 in the James Webb Space Telescope (JWST) NIRISS pre-imaging of the A2744 galaxy-cluster field. The star's background host galaxy lies on a fold caustic of the foreground lens, and the cluster creates a pair of images of the region close to the lensed star. We identified the bright transient in one of the merging images at a distance of similar to 0.'' 15 from the critical curve by subtracting the JWST F115W and F150W imaging from coadditions of archival Hubble Space Telescope (HST) F105W and F125W images and F140W and F160W images, respectively. Since the time delay between the two images should be only hours, the transient must be the microlensing event of an individual star, as opposed to a luminous stellar explosion that would persist for days to months. Analysis of individual exposures suggests that the star's magnification is not changing rapidly during the observations. From photometry of the point source through the F115W, F150W, and F200W filters, we identify a strong Balmer break, and modeling allows us to constrain the star's temperature to be approximately 7000-12,000 K.This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with program JWST-ERS-1324. The specific observations analyzed can be accessed via 10.17909/y6dh-6g16. We acknowledge financial support from NASA through grant JWST-ERS-1324. Archival images from the Hubble Space Telescope were also used. We would like to thank Dr. Pietro Bergamini, Prof. Piero Rosati, Prof. Claudio Grillo, Dr. Ana Acebron, and Dr. Eros Vanzella for their helpful comments on our paper and for sharing the predictions of their lens model.W.C. acknowledges support from NASA HST grant AR-15791. P.L.K. is supported by NSF grant AST-1908823 and NASA/Keck JPL RSA 1644110. R.A.W. acknowledges support from NASA JWST Interdisciplinary Scientist grants NAG5-12460, NNX14AN10G, and 80NSSC18K0200 from GSFC. J.M.D. acknowledges the support of project PGC2018-101814-B-100 (MCIU/AEI/MINECO/FEDER, UE) Ministerio de Ciencia, Investigacion y Universidades. This project was funded by the Agencia Estatal de Investigacion, Unidad de Excelencia Maria de Maeztu, ref. MDM-2017-0765. A.K. is supported by scientist grants NAG5-12460, NNX14AN10G, and 80NSSC18K0200 from GSFC. A.Z. and A.K.M. acknowledge support by Grant No. 2020750 from the United States-Israel Binational Science Foundation (BSF) and grant No. 2109066 from the United States National Science Foundation (NSF), and by the Ministry of Science & Technology, Israel. M.B. acknowledges support from the Slovenian national research agency ARRS through grant N1-0238
Early results from GLASS-JWST. III: Galaxy candidates at z9-15
We present the results of a first search for galaxy candidates at
z9--15 on deep seven-bands NIRCam imaging acquired as part of the
GLASS-JWST Early Release Science Program on a flanking field of the Frontier
Fields cluster A2744. Candidates are selected via two different renditions of
the Lyman-break technique, isolating objects at z9-11, and z9-15,
respectively, supplemented by photometric redshifts obtained with two
independent codes. We find six color-selected candidates at z9, plus one
additional candidate with photometric redshift z9. In particular,
we identify two bright candidates at that are
unambiguously placed at and , respectively. The
total number of galaxies discovered at is in line with the predictions of
a non-evolving LF. The two bright ones at are unexpected given the
survey volume, although cosmic variance and small number statistics limits
general conclusions. This first search demonstrates the unique power of JWST to
discover galaxies at the high redshift frontier. The candidates are ideal
targets for spectroscopic follow-up in cycle.Comment: Submitted to ApJL, 9 pages, 4 figure
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