We present time-series imaging polarimetry observations of a very nearby superluminous supernova 2018hti at z = 0.063, to probe its explosion mechanism and shed light on the energy source powering ...superluminous supernovae (SLSNe). We obtain linear polarimetry using the Alhambra Faint Object Spectrograph and Camera on board the 2.5 m Nordic Optical Telescope. Our observations show polarization at the ∼1.9% level before and after the supernova reached light-curve maximum. However, this level of polarization is consistent with the line-of-sight interstellar polarization; hence, the polarization from the supernovae itself was not detected at a level of >3 . This suggests that the explosion of SN 2018hti is almost spherical, similar to previous polarimetry studies of other SLSNe.
Abstract
In this paper we analyze Sloan
g,
r,
i
archival imaging data of M33 taken by Hartman et al. using MegaCam at the Canada–France–Hawaii Telescope. To determine the distance to the M33 galaxy, ...we performed several analytical steps to identify its Cepheid population. We used the Lomb–Scargle algorithm to find periodicity and visually identified 1989 periodic variable stars. Since Cepheids occupy a specific region of the color–magnitude diagram, to differentiate Cepheids from other variables we used the expected position of the Cepheid instability strip to down-select Cepheids in M33 from other variables. This led to our sample of 1622 variables, the largest Cepheid sample known in M33 to date. We further classified these Cepheids into different subclasses, and used the fundamental mode Cepheids to estimate distance moduli for M33 in different filters:
μ
= 25.044 ± 0.083 mag in the
g
filter,
μ
= 24.886 ± 0.074 mag in the
r
filter, and
μ
= 24.785 ± 0.068 mag for the
i
filter. These results are in agreement with previous results.
We present deep near-infrared spectroscopy of six quasars at 6.1 ≤ z ≤ 6.7 with Very Large Telescope/X-Shooter and Gemini-N/GNIRS. Our objects, originally discovered through a wide-field optical ...survey with the Hyper Suprime-Cam (HSC) Subaru Strategic Program (HSC-SSP), have the lowest luminosities (−25.5 mag ≤ M1450 ≤ −23.1 mag) of the z > 5.8 quasars with measured black hole (BH) masses. From single-epoch mass measurements based on Mg ii λ2798, we find a wide range in BH masses, from MBH = 107.6 to 109.3 M . The Eddington ratios Lbol/LEdd range from 0.16 to 1.1, but the majority of the HSC quasars are powered by MBH ∼ 109 M supermassive black holes (SMBHs) accreting at sub-Eddington rates. The Eddington ratio distribution of the HSC quasars is inclined to lower accretion rates than those of Willott et al., who measured the BH masses for similarly faint z ∼ 6 quasars. This suggests that the global Eddington ratio distribution is wider than has previously been thought. The presence of MBH ∼ 109 M SMBHs at z ∼ 6 cannot be explained with constant sub-Eddington accretion from stellar remnant seed BHs. Therefore, we may be witnessing the first buildup of the most massive BHs in the first billion years of the universe, the accretion activity of which is transforming from active growth to a quiescent phase. Measurements of a larger complete sample of z 6 low-luminosity quasars, as well as deeper observations with future facilities, will enable us to better understand the early SMBH growth in the reionization epoch.
We present imaging polarimetry observations of the recently discovered type I superluminous supernova 2020ank, in order to use (a)symmetry of the ejecta and SN photosphere that manifest themselves in ...the supernova lights as a probe of its explosion mechanism and investigate the energy sources that power the superluminous supernovae behind the scene. We have obtained linear imaging polarimetry in the optical with the Alhambra Faint Object Spectrograph and Camera mounted on the 2.5 m Nordic Optical Telescope. Our observations on March 1, 2020 manifest negligible polarization at 0.6 ± 0.3% level, shortly after the supernova reached its maximum brightness in mid‐February. The low degree of polarization implies that the explosion of SN 2020ank is nearly spherical; this is consistent with results of polarimetric observations of other superluminous supernovae at early epochs.
We present timely spectroscopic follow-ups of WG0214-2105, a background quasar strongly lensed by a foreground galaxy into four images. WG0204-2105 was recently identified by Agnello from a ...combination of the mid-infrared quasar color selection using WISE photometry and the exquisite astrometric resolution of Gaia, and can be clearly seen in the Dark Energy Survey, VST-ALTAS, and Pan-STARRS optical imaging. The quasar images are relatively faint, thus prompting us to conduct spectroscopic observations using the Gemini Multi-Object Spectrographs (GMOS) spectrograph on board the 8 m Gemini telescope. The GMOS spectra firmly detected the emission lines, e.g., Ly , C iv, and C iii, from the background quasar, allowing us to confirm the lensing nature and pin down the quasar redshifts to be z = 3.24. There are also absorption lines, putatively associated with a foreground absorber at z = 0.45. We also derive the broadband photometry of the quasar images using the Pan-STARRS grizy images, as well as the time-delay using the aforementioned redshifts. Future long-term photometric follow-up will help narrow down the time-delays, providing a firm basis to determine Hubble constant.
Superluminous supernovae (SLSNe) are found predominantly in dwarf galaxies, indicating that their progenitors have a low metallicity. However, the most nearby SLSN to date, SN 2017egm, occurred in ...the spiral galaxy NGC 3191, which has a relatively high stellar mass and correspondingly high metallicity. In this Letter, we present detailed analysis of the nearby environment of SN 2017egm using MaNGA IFU data, which provides spectral data on kiloparsec scales. From the velocity map we find no evidence that SN 2017egm occurred within some intervening satellite galaxy, and at the SN position most metallicity diagnostics yield a solar and above solar metallicity ( ). Additionally, we measure a small H equivalent width (EW) at the SN position of just 34 , which is one of the lowest EWs measured at any SLSN or gamma-ray burst position, and indicative of the progenitor star being comparatively old. We also compare the observed properties of NGC 3191 with other SLSN host galaxies. The solar-metallicity environment at the position of SN 2017egm presents a challenge to our theoretical understanding, and our spatially resolved spectral analysis provides further constraints on the progenitors of SLSNe.
Abstract
We describe the Arizona-NOIRLab Temporal Analysis and Response to Events System (ANTARES), a software instrument designed to process large-scale streams of astronomical time-domain alerts. ...With the advent of large-format CCDs on wide-field imaging telescopes, time-domain surveys now routinely discover tens of thousands of new events each night, more than can be evaluated by astronomers alone. The ANTARES event broker will process alerts, annotating them with catalog associations and filtering them to distinguish customizable subsets of events. We describe the data model of the system, the overall architecture, annotation, implementation of filters, system outputs, provenance tracking, system performance, and the user interface.
Biparental Inheritance of Mitochondrial DNA in Humans Luo, Shiyu; Valencia, C. Alexander; Zhang, Jinglan ...
Proceedings of the National Academy of Sciences - PNAS,
12/2018, Letnik:
115, Številka:
51
Journal Article
Recenzirano
Odprti dostop
Although there has been considerable debate about whether paternal mitochondrial DNA (mtDNA) transmission may coexist with maternal transmission of mtDNA, it is generally believed that mitochondria ...and mtDNA are exclusively maternally inherited in humans. Here, we identified three unrelated multigeneration families with a high level of mtDNA heteroplasmy (ranging from 24 to 76%) in a total of 17 individuals. Heteroplasmy of mtDNA was independently examined by high-depth whole mtDNA sequencing analysis in our research laboratory and in two Clinical Laboratory Improvement Amendments and College of American Pathologists-accredited laboratories using multiple approaches. A comprehensive exploration of mtDNA segregation in these families shows biparental mtDNA transmission with an autosomal dominantlike inheritance mode. Our results suggest that, although the central dogma of maternal inheritance of mtDNA remains valid, there are some exceptional cases where paternal mtDNA could be passed to the offspring. Elucidating the molecular mechanism for this unusual mode of inheritance will provide new insights into how mtDNA is passed on from parent to offspring and may even lead to the development of new avenues for the therapeutic treatment for pathogenic mtDNA transmission.
Display omitted
•The microtopography and surface characteristics of actual and replica shark skin were studied.•The effect of surface properties on bacterial attachment and biofilm formation were ...studied.•The microscale topography of shark skin slightly promoted bacterial attachment at an early stage•The rough characters of shark skin prevent bacteria from developing biofilms.
In this study, we investigate the microscale structure of shark skin denticles at abdomen (A) and fin (F) locations, analyze the roughness and wetting properties related to their microstructures, and evaluate the effect of the surface properties on early bacterial attachment and biofilm formation. Microstructural analysis by scanning electron microscopy and confocal laser scanning microscopy confirmed the length (A: 165–180 μm vs. F: 145–165 μm), width (A: 86–100 μm vs. F: 64–70 μm), height (A: 10.5–13.5 μm vs. F: 6.2–8.8 μm), and density (A: 110–130 denticles/mm2vs. F: 80–130 denticles/mm2) of the denticles. The results showed that the roughness and hydrophobicity properties were affected with slight differences in the microscale architecture. The denticles with a larger width, higher ridge, and denser overlap provided a rougher and more hydrophobic surface. The microscale structure not only affected surface properties but also the biological attachment process. The microscale topography of shark skin slightly promoted bacterial attachment at an early stage, but prevented bacteria from developing biofilms. This systematic investigation provides insights into the effects of the surface topography of shark skin on its anti-fouling mechanism, which will enable the future development of various products related to human activity, such as healthcare products, underwater devices and applications, and water treatment applications.
Detection of Diatomic Carbon in 2I/Borisov Lin, Hsing Wen; Lee, Chien-Hsiu; Gerdes, D. W. ...
Astrophysical journal. Letters,
02/2020, Letnik:
889, Številka:
2
Journal Article
Recenzirano
Odprti dostop
2I/Borisov is the first-ever observed interstellar comet (and the second detected interstellar object (ISO)). It was discovered on 2019 August 30 and has a heliocentric orbital eccentricity of ∼3.35, ...corresponding to a hyperbolic orbit that is unbound to the Sun. Given that it is an ISO, it is of interest to compare its properties-such as composition and activity-with the comets in our solar system. This study reports low-resolution optical spectra of 2I/Borisov. The spectra were obtained by the MDM Observatory Hiltner 2.4 m telescope/Ohio State Multi-Object Spectrograph (on 2019 October 31.5 and November 4.5, UT). The wavelength coverage spanned from 3700 to 9200 . The dust continuum reflectance spectra of 2I/Borisov show that the spectral slope is steeper in the blue end of the spectrum (compared to the red). The spectra of 2I/Borisov clearly show CN emission at 3880 , as well as C2 emission at both 4750 and 5150 . Using a Haser model to covert the observed fluxes into estimates for the molecular production rates, we find Q(CN) = 2.4 0.2 × 1024 s−1, and Q(C2) = (5.5 0.4) × 1023 s−1 at the heliocentric distance of 2.145 au. Our Q(CN) estimate is consistent with contemporaneous observations, and the Q(C2) estimate is generally below the upper limits of previous studies. We derived the ratio Q(C2)/Q(CN) = 0.2 0.1, which indicates that 2I/Borisov is depleted in carbon-chain species, but is not empty. This feature is not rare for the comets in our solar system, especially in the class of Jupiter-family comets.
PDF
