We have identified a new class of Asymptotic Giant Branch (AGB) stars in the Small and Large Magellanic Clouds (SMC/LMC) using optical to infrared photometry, light curves, and optical spectroscopy. The strong dust production and long-period pulsations of these stars indicate that they are at the very end of their AGB evolution. Period-mass-radius relations for the fundamental-mode pulsators give median current stellar masses of 1.14M_{sun}_ in the LMC and 0.94M_{sun}_ in the SMC (with dispersions of 0.21 and 0.18M_{sun}_, respectively), and models suggest initial masses of <1.5M_{sun}_ and <1.25 M_{sun}_, respectively. This new class of stars includes both O-rich and C-rich chemistries, placing the limit where dredge-up allows carbon star production below these masses. A high fraction of the brightest among them should show S star characteristics indicative of atmospheric C/O~1, and many will form O-rich dust prior to their C-rich phase. These stars can be separated from their less-evolved counterparts by their characteristically red J-[8] colors.
We present the first subarcsecond-resolution mid-infrared (MIR) atlas of local active galactic nuclei (AGN). Our atlas contains 253 AGN with a median redshift of z=0.016, and includes all publicly available MIR imaging performed to date with ground-based 8-m class telescopes, a total of 895 independent measurements. Of these, more than 60% are published here for the first time. We detect extended nuclear emission in at least 21% of the objects, while another 19% appear clearly point-like, and the remaining objects cannot be constrained. Where present, elongated nuclear emission aligns with the ionization cones in Seyferts. Subarcsecond resolution allows us to isolate the AGN emission on scales of a few tens of parsecs and to obtain nuclear photometry in multiple filters for the objects. Median spectral energy distributions (SEDs) for the different optical AGN types are constructed and individual MIR 12 and 18um continuum luminosities are computed. These range over more than six orders of magnitude. In comparison to the arcsecond-scale MIR emission as probed by Spitzer, the continuum emission is much lower on subarcsecond scales in many cases. The silicate feature strength is similar on both scales and generally appears in emission (absorption) in type I (II) AGN. However, the polycyclic aromatic hydrocarbon emission appears weaker or absent on subarcsecond scales. The differences of the MIR SEDs on both scales are particularly large for AGN/starburst composites and close-by (and weak) AGN. The nucleus dominates over the total emission of the galaxy only at luminosities >~10^44^erg/s. The AGN MIR atlas is well suited not only for detailed investigation of individual sources but also for statistical studies of AGN unification.
We performed a detailed photometric analysis of the lensed system UM673 (Q0142-100) and an analysis of the tentative lens models. High-resolution adaptive optics images of UM673 taken with the Subaru telescope in the H band were examined. We also analysed the J, H and K-band observational data of UM673 obtained with the 1.3m telescope at the CTIO observatory. We present photometry of quasar components A and B of UM673, the lens, and the nearby bright galaxy using H-band observational data obtained with the Subaru telescope. Based on the CTIO observations of UM673, we also present J- and H-band photometry and estimates of the J, H and K-band flux ratios between the two UM673 components in recent epochs. The near-infrared fluxes of the A and B components of UM673 and their published optical fluxes are analysed to measure extinction properties of the lensing galaxy. We estimate the extinction-corrected flux ratio between components A and B to be about 2.14 mag. We discuss lens models for the UM673 system constrained with the positions of the UM673 components, their flux ratio, and the previously measured time delay.
Recent spectroscopic observations of the outer halo globular cluster (GC) NGC 2419 show that it is unique among GCs, in terms of chemical abundance patterns, and some suggest that it was originated in the nucleus of a dwarf galaxy. Here we show, from the Subaru narrowband photometry employing a calcium filter, that the red giant branch (RGB) of this GC is split into two distinct subpopulations. Comparison with spectroscopy has confirmed that the redder RGB stars in the hk[=(Ca-b)-(b-y)] index are enhanced in [Ca/H] by ~0.2dex compared to the bluer RGB stars. Our population model further indicates that the calcium-rich second generation stars are also enhanced in helium abundance by a large amount ({Delta}Y=0.19). Our photometry, together with the results for other massive GCs (e.g., {omega} Cen, M22, and NGC 1851), suggests that the discrete distribution of RGB stars in the hk index might be a universal characteristic of this growing group of peculiar GCs. The planned narrowband calcium photometry for the Local Group dwarf galaxies would help to establish an empirical connection between these GCs and the primordial building blocks in the hierarchical merging paradigm of galaxy formation.
We find a new substellar companion to the Pleiades member star, Pleiades HII 3441, using the Subaru telescope with adaptive optics. The discovery is made as part of the high-contrast imaging survey to search for planetary-mass and substellar companions in the Pleiades and young moving groups. The companion has a projected separation of 0.49+/-0.02 (66+/-2au) and a mass of 68+/-5MJ based on three observations in the J-, H-, and Ks-bands. The spectral type is estimated to be M7 (~2700K), and thus no methane absorption is detected in the H band. Our Pleiades observations result in the detection of two substellar companions including one previously reported among 20 observed Pleiades stars, and indicate that the fraction of substellar companions in the Pleiades is about 10.0^+26.1^_-8.8_%. This is consistent with multiplicity studies of both the Pleiades stars and other open clusters.
We present a catalog of ultra-diffuse galaxies (UDGs) in the Coma cluster. UDGs are a subset of low surface brightness (SB) galaxies with very large effective radii defined by van Dokkum et al. (2015ApJ...798L..45V). We surveyed the Subaru data archive for deep Suprime-Cam/Subaru R-band images, and used data covering the 1.7x2.7{deg} region of the Coma cluster. The data are ~1 magnitude deeper than the data of van Dokkum et al. in limiting SB. This paper explains the details of our sample selection procedure. This UDG catalog includes positions, magnitudes, effective radii, mean and central SBs, and colors (when available). Comparisons with previous galaxy catalogs in the literature are performed, and we show that the current catalog is the largest for UDGs. We also discuss that most of the UDGs are members of the Coma cluster, and the major axis of the UDGs tends to align toward the cluster center (radial alignment).
We present luminosity functions (LFs) and various properties of Ly{alpha} emitters (LAEs) at z=3.1, 3.7, and 5.7, in a 1deg^2^ sky of the Subaru/XMM-Newton Deep Survey (SXDS) Field. We obtain a photometric sample of 858 LAE candidates based on deep Subaru Suprime-Cam imaging data and a spectroscopic sample of 84 confirmed LAEs from Subaru FOCAS and VLT VIMOS spectroscopy in a survey volume of ~10^6^Mpc^3^ with a limiting Ly{alpha} luminosity of ~3x10^42^ergs/s. We derive the LFs of the Ly{alpha} and UV continuum (~1500{AA}) for each redshift, taking into account the statistical error and the field-to-field variation. We identify six LAEs with AGN activities from our spectra combined with VLA, Spitzer, and XMM-Newton data. Among the photometrically selected LAEs at z=3.1 and 3.7, only ~1% show AGN activities, while the brightest LAEs with logL(Ly{alpha})>~43.4-43.6ergs/s appear to always host AGNs. Our LAEs are bluer in UV-continuum color than dropout galaxies, suggesting lower extinction and/or younger stellar populations.
We present multi-wave band optical imaging data obtained from observations of the Subaru/XMM-Newton Deep Survey (SXDS). The survey field, centered at RA=02:18:00, DE=-05:00:00, has been the focus of a wide range of multiwavelength observing programs spanning from X-ray to radio wavelengths. A large part of the optical imaging observations are carried out with Suprime-Cam on Subaru Telescope at Mauna Kea in the course of Subaru Telescope "Observatory Projects".
We present a spectroscopic analysis of nearly 8000 late-type dwarfs in the Sloan Digital Sky Survey. Using the H{alpha} emission line as an activity indicator, we investigate the fraction of active stars as a function of spectral type and find a peak near type M8, confirming previous results.
The Herschel Reference Survey (HRS) is a guaranteed time Herschel key project aimed at studying the physical properties of the interstellar medium in galaxies of the nearby universe. This volume limited, K-band selected sample is composed of galaxies spanning the whole range of morphological types (from ellipticals to late-type spirals) and environments (from the field to the centre of the Virgo Cluster). We present flux density measurements of the whole sample of 323 galaxies of the HRS in the three bands of the Spectral and Photometric Imaging Receiver (SPIRE), at 250um, 350um and 500um. Aperture photometry is performed on extended galaxies and point spread function (PSF) fitting on timeline data for unresolved objects; we carefully estimate errors and upper limits. The flux densities are found to be in good agreement with those of the HeViCS and KINGFISH key projects in all SPIRE bands, and of the Planck consortium at 350um and 550um, for the galaxies in common. This submillimetre catalogue of nearby galaxies is a benchmark for the study of the dust properties in the local universe, giving the zero redshift reference for any cosmological survey.
