Search

We report the first detection of a credible progenitor system for a Type Ic supernova (SN Ic), SN 2017ein. We present spectra and photometry of the SN, finding it to be similar to carbon-rich, low-luminosity SNe Ic. Using a post-explosion Keck adaptive optics image, we precisely determine the position of SN 2017ein in pre-explosion HST images, finding a single source coincident with the SN position. This source is marginally extended, and is consistent with being a stellar cluster. However, under the assumption that the emission of this source is dominated by a single point source, we perform point-spread function photometry, and correcting for line-of-sight reddening, we find it to have M F555W = −7.5 ± 0.2 mag and m F555W − m F814W=−0.67 ± 0.14 mag. This source is bluer than the main sequence and brighter than almost all Wolf–Rayet stars, however, it is similar to some WC+O− and B-star binary systems. Under the assumption that the source is dominated by a single star, we find that it had an initial mass of $$55^{+20}_{-15} \rm M_{\odot}$$. We also examined binary star models to look for systems that match the overall photometry of the pre-explosion source and found that the best-fitting model is an 80+48M⊙ close binary system in which the 80M⊙ star is stripped and explodes as a lower mass star. Late-time photometry after the SN has faded will be necessary to cleanly separate the progenitor star emission from the additional coincident emission. [ABSTRACT FROM AUTHOR]

We present a detection in pre-explosion Hubble Space Telescope (HST) imaging of a point source consistent with being the progenitor star of the Type IIb supernova (SN IIb) 2016gkg. Post-explosion imaging from the Keck adaptive optics system was used to perform relative astrometry between the Keck and HST imaging. We identify a single point source in the HST images coincident with the SN position to 0.89σ. The HST photometry is consistent with the progenitor star being an A0 Ia star with T = 9500 K and log (L/Lʘ) = 5.15. We find that the SN 2016gkg progenitor star appears more consistent with binary than single-star evolutionary models. In addition, early-time light-curve data from SN 2016gkg revealed a rapid rise in luminosity within ~0.4?d of non-detection limits, consistent with models of the cooling phase after shock break-out. We use these data to determine an explosion date of 2016 September 20.15 and progenitor-star radius of log?(R/Rʘ) = 2.41, which agrees with photometry from the progenitor star. Our findings are also consistent with detections of other SNe IIb progenitor stars, although more luminous and bluer than most other examples. [ABSTRACT FROM AUTHOR]

We present near-infrared imaging and integral field spectroscopy of the centre of the dusty luminous infrared galaxy merger MCG+08-11-002, taken using the Near InfraRed Camera 2 (NIRC2) and the OH-Suppressing InfraRed Imaging Spectrograph (OSIRIS) on Keck II. We achieve a spatial resolution of ~25 pc in the K band, allowing us to resolve 41 star clusters in the NIRC2 images. We calculate the ages of 22/25 star clusters within the OSIRIS field using the equivalent widths of the CO 2.3 μm absorption feature and the Br γ nebular emission line. The star cluster age distribution has a clear peak at ages ≲20 Myr, indicative of current starburst activity associated with the final coalescence of the progenitor galaxies. There is a possible second peak at ~65 Myr which may be a product of the previous close passage of the galaxy nuclei. We fit single and double starburst models to the star cluster age distribution and use Monte Carlo sampling combined with two-sided Kolmogorov-Smirnov tests to calculate the probability that the observed data are drawn from each of the best-fitting distributions. There is a >90 per cent chance that the data are drawn from either a single or double starburst star formation history, but stochastic sampling prevents us from distinguishing between the two scenarios. Our analysis of MCG+08-11-002 indicates that star cluster age distributions provide valuable insights into the timelines of galaxy interactions and may therefore play an important role in the future development of precise merger stage classification systems. [ABSTRACT FROM AUTHOR]

We combine optical and near-infrared adaptive optics-assisted integral field observations of the merging ultraluminous infrared galaxies IRAS F17207-0014 from the Wide-Field Spectrograph and Keck/OH-Suppressing Infra-Red Imaging Spectrograph (OSIRIS). The optical emission line ratios [N II]/Hα, [S II]/Hα, and [O I]/Hα reveal a mixing sequence of shocks present throughout the galaxy, with the strongest contributions coming from large radii (up to 100 per cent at ∼5 kpc in some directions), suggesting galactic-scale winds. The near-infrared observations, which have approximately 30 times higher spatial resolution, show that two sorts of shocks are present in the vicinity of the merging nuclei: low-level shocks distributed throughout our field-of-view evidenced by an H2/Brγ line ratio of ∼0.6-4, and strong collimated shocks with a high H2/Brγ line ratio of ∼4-8, extending south from the two nuclear discs approximately 400 pc (∼0.5 arcsec). Our data suggest that the diffuse shocks are caused by the collision of the interstellar media associated with the two progenitor galaxies and the strong shocks trace the base of a collimated outflow coming from the nucleus of one of the two discs. [ABSTRACT FROM AUTHOR]

When galaxies merge, gas accretes onto both central supermassive black holes. Thus, one expects to see dual active galactic nuclei (AGNs) in a fraction of galaxy mergers. Candidates for galaxies containing dual AGNs have been identified by the presence of double-peaked narrow [O III] emission lines and by high spatial resolution images of close galaxy pairs. 30% of double-peaked narrow [OIII] emission line SDSS AGNs have two spatial components within a 3″ radius. However, spatially resolved spectroscopy is needed to confirm these galaxy pairs as systems with double AGNs. With the Keck 2 Laser Guide Star Adaptive Optics system and the OSIRIS near-infrared integral field spectrograph, we obtained spatially resolved spectra for SDSS J095207.62+255257.2, confirming that it contains a Type 1 and a Type 2 AGN separated by 4.8 kpc (=1.0″). We performed similar integral field and long-slit spectroscopy observations of more spatially separated candidate dual AGNs and will report on the varied results. By assessing what fraction of radio-quiet double-peaked emission line SDSS AGNs are true dual AGNs, we can better constrain the statistics of dual AGNs and characterize physical conditions throughout these interacting AGNs. [ABSTRACT FROM PUBLISHER]

Whereas the situation of the Jews in the Medieval Crown of Aragon is often considered favourable compared to other places, there were still some episodes of recurrent violence towards them. The stoning of their persons and their goods during the celebration of the Easter Festival raises the question of the function of ritual violence—if it is violence of that kind—in this territory. This paper examines the positions of the different sources of authority towards these episodes, and how they could use them to demonstrate their power. The interactions between the King, the Church and the population were at stake. Jewish ritual violence and the reactions it provoked among Jews and Christians can be observed thanks to both Latin and Hebrew sources. [ABSTRACT FROM AUTHOR]

A model for planar laser-driven ablation is presented, including the effects of inhibited electron thermal conduction. Localized deposition of laser energy at the critical-density surface is assumed. A steady-state solution in the conduction zone is joined to a rarefaction wave in the underdense corona. The global flow structure is calculated, as well as the ablation pressure, ablation rate, and hydrodynamic efficiency. Criteria are developed for the importance of the inertial force caused by the acceleration of the slab. The results agree well with time-dependent computer simulations using a Lagrangian hydrodynamics code. [ABSTRACT FROM AUTHOR]

Recent experiments performed at École Polytechnique on the wavelength scaling of laser light absorption by flat plastic targets are presented and interpreted. The measurements show larger absorption fractions for shorter laser wavelengths, lower laser intensities, and longer laser pulse lengths. These experiments are analyzed using computer hydrodynamics codes, and show that there are two possible physics models consistent with the data: (1) Inhibited electron heat flow together with absorption rates higher than those predicted by resonance absorption and inverse bremsstrahlung. (2) Nearly classical heat flow, with no additional enhancement in the absorption rate. [ABSTRACT FROM AUTHOR]

The NSF Science and Technology Center for Adaptive Optics (CfAO) is supporting a major scientific legacy project called the CfAO Treasury Survey (CATS). CATS is obtaining near-infrared AO data in deep HST survey fields, such as GEMS, GOODS-N, & EGS. Besides summarizing the main objectives of CATS, we highlight some recent imaging work on the study of distant field galaxies, AGNs, and a redshift z = 1.32 supernova. CATS plans the first data release to the community in early 2007 (check http://www.astro.ucla.edu/~irlab/cats/index.shtml for more details on CATS and latest updates). [ABSTRACT FROM PUBLISHER]

The Center for Adaptive Optics (CfAO) Treasury Survey (CATS) has observed 11 Chandra sources (10 AGN) at z ~ 1 in the GOODS-South field with the laser guide star adaptive optics (LGSAO) system at Keck Observatory. We combine this K band imaging with ACS imaging in the B, V, I, and z bands to obtain multi-color imaging at a spatial resolution better than 100 mas in all bands. We attempt to remove central optical point sources from AGN using the GALFIT (Peng et al. 2002) routine. We fit Bruzual & Charlot (2003) tau-models to the residuals and find young, dusty stellar populations in the central 1-2 kpc (the mean central optical depth at rest-frame 500 nm is 4-5). [ABSTRACT FROM PUBLISHER]

Using adaptive optics on the W. M. Keck II telescope, we imaged Titan several times during 1999 to 2001 in narrowband near-infrared filters selected to probe Titan''s stratosphere and upper troposphere. We observed a bright feature around the south pole, possibly a collar of haze or clouds. Further, we find that solar phase angle explains most of the observed east–west brightness asymmetry of Titan''s atmosphere, although the data do not preclude the presence of a “morning fog” effect at small solar phase angle. [Copyright &y& Elsevier]