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We report the discovery of an SN 1988Z–like type IIn supernova KISS15s found in a low-mass star-forming galaxy at redshift z = 0.038 during the course of the Kiso Supernova Survey (KISS). KISS15s shows long-duration optical continuum and emission line light curves, indicating that KISS15s is powered by a continuous interaction between the expanding ejecta and dense circumstellar medium (CSM). The Hα emission line profile can be decomposed into four Gaussians of narrow, intermediate, blueshifted intermediate, and broad velocity width components, with a full width at half maximum of ≲100, ∼2000, and ∼14,000 km s−1 for the narrow, intermediate, and broad components, respectively. The presence of the blueshifted intermediate component, of which the line-of-sight velocity relative to the systemic velocity is about −5000 km s−1, suggests that the ejecta-CSM interaction region has an inhomogeneous morphology and anisotropic expansion velocity. We found that KISS15s shows increasing infrared continuum emission, which can be interpreted as hot dust thermal emission of T ∼ 1200 K from newly formed dust in a cool, dense shell in the ejecta-CSM interaction region. The progenitor mass-loss rate, inferred from bolometric luminosity, is , where vw is the progenitor’s stellar wind velocity. This implies that the progenitor of KISS15s was a red supergiant star or a luminous blue variable that had experienced a large mass loss in the centuries before the explosion. [ABSTRACT FROM AUTHOR]

We present the Hα intensity map of the host galaxy of the repeating fast radio burst FRB 121102 at a redshift of z = 0.193 obtained with the AO-assisted Kyoto 3DII optical integral-field unit mounted on the 8.2 m Subaru Telescope. We detected a compact Hα-emitting (i.e., star-forming) region in the galaxy, which has a much smaller angular size ( (1.9 kpc) at full width at half maximum (FWHM)) than the extended stellar continuum emission region determined by the Gemini/GMOS -band image ( (4.6 kpc) at FWHM with ellipticity ). The spatial offset between the centroid of the Hα emission region and the position of the radio bursts is (0.26 ± 0.07 kpc), indicating that FRB 121102 is located within the star-forming region. This close spatial association of FRB 121102 with the star-forming region is consistent with expectations from young pulsar/magnetar models for FRB 121102, and it also suggests that the observed Hα emission region can make a major dispersion measure (DM) contribution to the host galaxy DM component of FRB 121102. Nevertheless, the largest possible value of the DM contribution from the Hα emission region inferred from our observations still requires a significant amount of ionized baryons in intergalactic medium (IGM; the so-called “missing” baryons) as the DM source of FRB 121102, and we obtain a 90% confidence level lower limit on the cosmic baryon density in the IGM in the low-redshift universe as . [ABSTRACT FROM AUTHOR]

We compare the isophote shape parameter a4 of early-type galaxies (ETGs) between z ∼ 1 and 0 as a proxy for dynamics to investigate the epoch at which the dynamical properties of ETGs are established, using cluster ETG samples with stellar masses of which have spectroscopic redshifts. We have 130 ETGs from the Hubble Space Telescope Cluster Supernova Survey for z ∼ 1 and 355 ETGs from the Sloan Digital Sky Survey for z ∼ 0. We have developed an isophote shape analysis method, which can be used for high-redshift galaxies and has been carefully compared with published results. We have applied the same method for both the z ∼ 1 and 0 samples. We find similar dependence of the a4 parameter on the mass and size at z ∼ 1 and 0; the main population of ETGs changes from disky to boxy at a critical stellar mass of with the massive end dominated by boxy. The disky ETG fraction decreases with increasing stellar mass both at z ∼ 1 and 0, and is consistent between these redshifts in all stellar mass bins when the Eddington bias is taken into account. Although uncertainties are large, the results suggest that the isophote shapes and probably dynamical properties of ETGs in massive clusters are already in place at z > 1 and do not significantly evolve in z < 1, despite significant size evolution in the same galaxy population. The constant disky fraction favors less violent processes than mergers as the main cause of the size and morphological evolution of intermediate mass ETGs in z < 1. [ABSTRACT FROM AUTHOR]