Abstract We use a multilevel perceptron (MLP) neural network to obtain photometry of saturated stars in the All-Sky Automated Survey for Supernovae (ASAS-SN). The MLP can obtain fairly unbiased ...photometry for stars from g ≃ 4 to 14 mag, particularly compared to the dispersion (15%–85% 1 σ range around the median) of 0.12 mag for saturated ( g < 11.5 mag) stars. More importantly, the light curve of a nonvariable saturated star has a median dispersion of only 0.037 mag. The MLP light curves are, in many cases, spectacularly better than those provided by the standard ASAS-SN pipelines. While the network was trained on g -band data from only one of ASAS-SN’s 20 cameras, initial experiments suggest that it can be used for any camera and the older ASAS-SN V -band data as well. The dominant problems seem to be associated with correctable issues in the ASAS-SN data reduction pipeline for saturated stars more than the MLP itself. The method is publicly available as a light-curve option on ASAS-SN Sky Patrol v1.0.
We analyzed the microlensing of the X-ray and optical emission of the lensed quasar PG 1115+080. We find that the effective radius of the X-ray emission is image dex smaller than that of the optical ...emission. Viewed as a thin disk observed at inclination angle i, the optical accretion disk has a scale length, defined by the point where the disk temperature matches the rest-frame energy of the monitoring band (image with image mum), of image. The X-ray emission region (1.4-21.8 keV in the rest frame) has an effective half-light radius of image. Given an estimated black hole mass of image, corresponding to a gravitational radius of image, the X-ray emission is generated near the inner edge of the disk, while the optical emission comes from scales slightly larger than those expected for an Eddington-limited thin disk. We find a weak trend supporting models with low stellar mass fractions near the lensed images, in mild contradiction to inferences from the stellar velocity dispersion and the time delays.
We present 13 seasons of R-band photometry of the quadruply lensed quasar WFI 2033-4723 from the 1.3 m SMARTS telescope at CTIO and the 1.2 m Euler Swiss Telescope at La Silla, in which we detect ...microlensing variability of ∼0.2 mag on a timescale of ∼6 years. Using a Bayesian Monte Carlo technique, we analyze the microlensing signal to obtain a measurement of the size of this system's accretion disk of at λrest = 2481 , assuming a 60° inclination angle. We confirm previous measurements of the BC and AB time delays, and we obtain a tentative measurement of the delay between the closely spaced A1 and A2 images of days. We conclude with an update to the Quasar Accretion Disk Size-Black Hole Mass Relation, in which we confirm that the accretion disk size predictions from simple thin disk theory are too small.
Abstract We present JWST MIRI 5.6, 10, and 21 μ m observations of the candidate failed supernova N6946-BH1 along with Hubble Space Telescope (HST) WFPC/IR 1.1 and 1.6 μ m data and ongoing optical ...monitoring data with the Large Binocular Telescope. There is a very red, dusty source at the location of the candidate, which has only ∼10%–15% of the luminosity of the progenitor star. The source is very faint in the HST near-IR observations (∼10 3 L ⊙ ) and is not optically variable to a limit of ∼10 3 L ⊙ at the R band. The dust is likely silicate and probably has to be dominated by very large grains, as predicted for dust formed in a failed supernova. The required visual optical depths are modest, so it should begin to significantly brighten in the near-IR over the next few years.
Abstract
We present a morphological study of the 17 lensed Ly
α
emitter (LAE) galaxies of the Baryon Oscillation Spectroscopic Survey Emission-Line Lens Survey (BELLS) for the GALaxy-Ly
α
EmitteR ...sYstems (BELLS GALLERY) sample. This analysis combines the magnification effect of strong galaxy–galaxy lensing with the high resolution of the
Hubble Space Telescope
to achieve a physical resolution of ∼80 pc for this 2 <
z
< 3 LAE sample, allowing a detailed characterization of the LAE rest-frame ultraviolet continuum surface brightness profiles and substructure. We use lens-model reconstructions of the LAEs to identify and model individual clumps, which we subsequently use to constrain the parameters of a generative statistical model of the LAE population. Since the BELLS GALLERY sample is selected primarily on the basis of Ly
α
emission, the LAEs that we study here are likely to be directly comparable to those selected in wide-field, narrowband LAE surveys, in contrast with the lensed LAEs identified in cluster-lensing fields. We find an LAE clumpiness fraction of approximately 88%, which is significantly higher than that found in previous (non-lensing) studies. We find a well-resolved characteristic clump half-light radii of ∼350 pc, a scale comparable to the largest H
ii
regions seen in the local universe. This statistical characterization of LAE surface-brightness profiles will be incorporated into future lensing analyses using the BELLS GALLERY sample to constrain the incidence of dark-matter substructure in the foreground lensing galaxies.
ABSTRACT
We present
Hubble Space Telescope
F606W-band imaging observations of 21 galaxy-Ly
α
emitter lens candidates in the Baryon Oscillation Spectroscopic Survey Emission-Line Lens Survey (BELLS) ...for the GALaxy-Ly
α
EmitteR sYstems (BELLS GALLERY) survey. Seventeen systems are confirmed to be definite lenses with unambiguous evidence of multiple imaging. The lenses are primarily massive early-type galaxies (ETGs) at redshifts of approximately 0.55, while the lensed sources are Ly
α
emitters (LAEs) at redshifts from two to three. Although most of the lens systems are well fit by smooth lens models consisting of singular isothermal ellipsoids in an external shear field, a thorough exploration of dark substructures in the lens galaxies is required. The Einstein radii of the BELLS GALLERY lenses are, on average, 60% larger than those of the BELLS lenses because of the much higher source redshifts. This will allow for a detailed investigation of the radius evolution of the mass profile in ETGs. With the aid of the average ∼13× lensing magnification, the LAEs are frequently resolved into individual star-forming knots with a wide range of properties. They have characteristic sizes from less than 100 pc to several kiloparsecs, rest-frame far-UV apparent AB magnitudes from 29.6 to 24.2, and typical projected separations of 500 pc to 2 kpc.
ABSTRACT
We present the first satellite system of the Large Binocular Telescope Satellites Of Nearby Galaxies Survey (LBT-SONG), a survey to characterize the close satellite populations of Large ...Magellanic Cloud to Milky-Way-mass, star-forming galaxies in the Local Volume. In this paper, we describe our unresolved diffuse satellite finding and completeness measurement methodology and apply this framework to NGC 628, an isolated galaxy with ∼1/4 the stellar mass of the Milky Way. We present two new dwarf satellite galaxy candidates: NGC 628 dwA, and dwB with MV = −12.2 and −7.7, respectively. NGC 628 dwA is a classical dwarf while NGC 628 dwB is a low-luminosity galaxy that appears to have been quenched after reionization. Completeness corrections indicate that the presence of these two satellites is consistent with CDM predictions. The satellite colours indicate that the galaxies are neither actively star forming nor do they have the purely ancient stellar populations characteristic of ultrafaint dwarfs. Instead, and consistent with our previous work on the NGC 4214 system, they show signs of recent quenching, further indicating that environmental quenching can play a role in modifying satellite populations even for hosts smaller than the Milky Way.
ABSTRACT
The scaling of the specific Type Ia supernova (SN Ia) rate with host galaxy stellar mass $\dot{\text{N}}_\text{Ia} / \text{M}_\star \sim \text{M}_\star ^{-0.3}$ as measured in ASAS-SN and ...DES strongly suggests that the number of SNe Ia produced by a stellar population depends inversely on its metallicity. We estimate the strength of the required metallicity dependence by combining the average star formation histories (SFHs) of galaxies as a function of their stellar mass with the mass–metallicity relation (MZR) for galaxies and common parametrizations for the SN Ia delay-time distribution. The differences in SFHs can account for only ∼30 per cent of the increase in the specific SN Ia rate between stellar masses of M⋆ = 1010 and 107.2 M⊙. We find that an additional metallicity dependence of approximately ∼Z−0.5 is required to explain the observed scaling. This scaling matches the metallicity dependence of the close binary fraction observed in APOGEE, suggesting that the enhanced SN Ia rate in low-mass galaxies can be explained by a combination of their more extended SFHs and a higher binary fraction due to their lower metallicities. Due to the shape of the MZR, only galaxies below M⋆ ≈ 3 × 109 M⊙ are significantly affected by the metallicity-dependent SN Ia rates. The $\dot{\text{N}}_\text{Ia} / \text{M}_\star \sim \text{M}_\star ^{-0.3}$ scaling becomes shallower with increasing redshift, dropping by factor of ∼2 at 107.2 M⊙ between z = 0 and 1 with our ∼Z−0.5 scaling. With metallicity-independent rates, this decrease is a factor of ∼3. We discuss the implications of metallicity-dependent SN Ia rates for one-zone models of galactic chemical evolution.
We present a catalog of 25 definite and 11 probable strong galaxy-galaxy gravitational lens systems with lens redshifts 0.4 z 0.7, discovered spectroscopically by the presence of higher-redshift ...emission lines within the Baryon Oscillation Spectroscopic Survey (BOSS) of luminous galaxies, and confirmed with high-resolution Hubble Space Telescope (HST) images of 44 candidates. Our survey extends the methodology of the Sloan Lens Advanced Camera for Surveys survey (SLACS) to higher redshift. We describe the details of the BOSS spectroscopic candidate detections, our HST ACS image processing and analysis methods, and our strong gravitational lens modeling procedure. We report BOSS spectroscopic parameters and ACS photometric parameters for all candidates, and mass-distribution parameters for the best-fit singular isothermal ellipsoid models of definite lenses. Our sample to date was selected using only the first six months of BOSS survey-quality spectroscopic data. The full five-year BOSS database should produce a sample of several hundred strong galaxy-galaxy lenses and in combination with SLACS lenses at lower redshift, strongly constrain the redshift evolution of the structure of elliptical, bulge-dominated galaxies as a function of luminosity, stellar mass, and rest-frame color, thereby providing a powerful test for competing theories of galaxy formation and evolution.
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