Shock Breakout in Type II Plateau Supernovae: Prospects for High Redshift Supernova Surveys

Shock breakout is the brightest radiative phenomenon in a supernova (SN) but is difficult to be observed owing to the short duration and X-ray/ultraviolet (UV)-peaked spectra. After the first observation from the rising phase reported in 2008, its observability at high redshift is attracting enormous attention. We perform multigroup radiation hydrodynamics calculations of explosions for evolutionary presupernova models with various main-sequence masses $M_{\rm MS}$, metallicities $Z$, and explosion energies $E$. We present multicolor light curves of shock breakout in Type II plateau SNe, being the most frequent core-collapse SNe, and predict apparent multicolor light curves of shock breakout at various redshifts $z$. We derive the observable SN rate and reachable redshift as functions of filter $x$ and limiting magnitude $m_{x,{\rm lim}}$ by taking into account an initial mass function, cosmic star formation history, intergalactic absorption, and host galaxy extinction. We propose a realistic survey strategy optimized for shock breakout. For example, the $g'$-band observable SN rate for $m_{g',{\rm lim}}=27.5$ mag is 3.3 SNe degree$^{-2}$ day$^{-1}$ and a half of them locates at $z\geq1.2$. It is clear that the shock breakout is a beneficial clue to probe high-$z$ core-collapse SNe. We also establish ways to identify shock breakout and constrain SN properties from the observations of shock breakout, brightness, time scale, and color. We emphasize that the multicolor observations in blue optical bands with $\sim$ hour intervals, preferably over $\geq2$ continuous nights, are essential to efficiently detect, identify, and interpret shock breakout.Comment: 26 pages, 23 figures. Accepted for publication in the Astrophysical Journal Supplement Serie

The Subaru/XMM-Newton Deep Survey (SXDS) - VI. Properties of Active Galactic Nuclei Selected by Optical Variability

We present the properties of active galactic nuclei (AGN) selected by optical variability in the Subaru/XMM-Newton Deep Field (SXDF). Based on the locations of variable components and light curves, 211 optically variable AGN were reliably selected. We made three AGN samples; X-ray detected optically non-variable AGN (XA), X-ray detected optically variable AGN (XVA), and X-ray undetected optically variable AGN (VA). In the VA sample, we found a bimodal distribution of the ratio between the variable component flux and the host flux. One of these two components in the distribution, a class of AGN with a faint variable component $i'_{\rm{vari}}\sim25$ mag in bright host galaxies $i'\sim21$ mag, is not seen in the XVA sample. These AGN are expected to have low Eddington ratios if we naively consider a correlation between bulge luminosity and black hole mass. These galaxies have photometric redshifts $z_{\rm{photo}}\sim0.5$ and we infer that they are low-luminosity AGN with radiatively inefficient accretion flows (RIAFs). The properties of the XVA and VA objects and the differences from those of the XA objects can be explained within the unified scheme for AGN. Optical variability selection for AGN is an independent method and could provide a complementary AGN sample which even deep X-ray surveys have not found.Comment: 9 pages, 10 figures, accepted for publication in Ap

CO Multi-line Imaging of Nearby Galaxies (COMING). IX. 12^{12}CO(JJ=2-1)/12^{12}CO(JJ=1-0) line ratio on kiloparsec scales

While molecular gas mass is usually derived from $^{12}$CO($J$=1-0) - the most fundamental line to explore molecular gas - it is often derived from $^{12}$CO($J$=2-1) assuming a constant $^{12}$CO($J$=2-1)/$^{12}$CO($J$=1-0) line ratio ($R_{2/1}$). We present variations of $R_{2/1}$ and effects of the assumption that $R_{2/1}$ is a constant in 24 nearby galaxies using $^{12}$CO data obtained with the Nobeyama 45-m radio telescope and IRAM 30-m telescope. The median of $R_{2/1}$ for all galaxies is 0.61, and the weighted mean of $R_{2/1}$ by $^{12}$CO($J$=1-0) integrated-intensity is 0.66 with a standard deviation of 0.19. The radial variation of $R_{2/1}$ shows that it is high (~0.8) in the inner ~1 kpc while its median in disks is nearly constant at 0.60 when all galaxies are compiled. In the case that the constant $R_{2/1}$ of 0.7 is adopted, we found that the total molecular gas mass derived from $^{12}$CO($J$=2-1) is underestimated/overestimated by ~20%, and at most by 35%. The scatter of a molecular gas surface density within each galaxy becomes larger by ~30%, and at most by 120%. Indices of the spatially resolved Kennicutt-Schmidt relation by $^{12}$CO($J$=2-1) are underestimated by 10-20%, at most 39% in 17 out of 24 galaxies. $R_{2/1}$ has good positive correlations with star-formation rate and infrared color, and a negative correlation with molecular gas depletion time. There is a clear tendency of increasing $R_{2/1}$ with increasing kinetic temperature ($T_{\rm kin}$). Further, we found that not only $T_{\rm kin}$ but also pressure of molecular gas is important to understand variations of $R_{2/1}$. Special considerations should be made when discussing molecular gas mass and molecular gas properties inferred from $^{12}$CO($J$=2-1) instead of $^{12}$CO($J$=1-0).Comment: 29 pages, 18 figures, 5 tables. Accepted for publication in PASJ. The original resolution version is available here (https://astro3.sci.hokudai.ac.jp/~radio/coming/publications/COMING_IX_org_res.pdf

Discovery of Four Gravitationally Lensed Quasars from the Sloan Digital Sky Survey

We present the discovery of four gravitationally lensed quasars selected from the spectroscopic quasar catalog of the Sloan Digital Sky Survey. We describe imaging and spectroscopic follow-up observations that support the lensing interpretation of the following four quasars: SDSS J0832+0404 (image separation \theta=1.98", source redshift z_s=1.115, lens redshift z_l=0.659); SDSS J1216+3529 (\theta=1.49", z_s=2.012); SDSS J1322+1052 (\theta=2.00", z_s=1.716); and SDSS J1524+4409 (\theta=1.67", z_s=1.210, z_l=0.320). Each system has two lensed images. We find that the fainter image component of SDSS J0832+0404 is significantly redder than the brighter component, perhaps because of differential reddening by the lensing galaxy. The lens potential of SDSS J1216+3529 might be complicated by the presence of a secondary galaxy near the main lensing galaxy.Comment: 25 pages, 10 figures, 6 tables, accepted for publication in A

Spectra and Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2 Compilation

We report on work to increase the number of well-measured Type Ia supernovae (SNe Ia) at high redshifts. Light curves, including high signal-to-noise HST data, and spectra of six SNe Ia that were discovered during 2001 are presented. Additionally, for the two SNe with z>1, we present ground-based J-band photometry from Gemini and the VLT. These are among the most distant SNe Ia for which ground based near-IR observations have been obtained. We add these six SNe Ia together with other data sets that have recently become available in the literature to the Union compilation (Kowalski et al. 2008). We have made a number of refinements to the Union analysis chain, the most important ones being the refitting of all light curves with the SALT2 fitter and an improved handling of systematic errors. We call this new compilation, consisting of 557 supernovae, the Union2 compilation. The flat concordance LambdaCDM model remains an excellent fit to the Union2 data with the best fit constant equation of state parameter w=-0.997^{+0.050}_{-0.054} (stat) ^{+0.077}_{-0.082} (stat+sys\ together) for a flat universe, or w=-1.035^{+0.055}_{-0.059} (stat)^{+0.093}_{-0.097} (stat+sys together) with curvature. We also present improved constraints on w(z). While no significant change in w with redshift is detected, there is still considerable room for evolution in w. The strength of the constraints depend strongly on redshift. In particular, at z > 1, the existence and nature of dark energy are only weakly constrained by the data.Comment: 33 pages, 18 figures; accepted for publication in Astrophysical Journal. For data tables, code for cosmological analysis and full-resolution figures, see http://supernova.lbl.gov/Union

The Sloan Digital Sky Survey Quasar Lens Search. III. Constraints on Dark Energy from the Third Data Release Quasar Lens Catalog

We present cosmological results from the statistics of lensed quasars in the Sloan Digital Sky Survey (SDSS) Quasar Lens Search. By taking proper account of the selection function, we compute the expected number of quasars lensed by early-type galaxies and their image separation distribution assuming a flat universe, which is then compared with 7 lenses found in the SDSS Data Release 3 to derive constraints on dark energy under strictly controlled criteria. For a cosmological constant model (w=-1) we obtain \Omega_\Lambda=0.74^{+0.11}_{-0.15}(stat.)^{+0.13}_{-0.06}(syst.). Allowing w to be a free parameter we find \Omega_M=0.26^{+0.07}_{-0.06}(stat.)^{+0.03}_{-0.05}(syst.) and w=-1.1\pm0.6(stat.)^{+0.3}_{-0.5}(syst.) when combined with the constraint from the measurement of baryon acoustic oscillations in the SDSS luminous red galaxy sample. Our results are in good agreement with earlier lensing constraints obtained using radio lenses, and provide additional confirmation of the presence of dark energy consistent with a cosmological constant, derived independently of type Ia supernovae.Comment: 9 pages, 3 figures, 2 tables, accepted for publication in A

A giant molecular cloud catalogue in the molecular disc of the elliptical galaxy NGC5128 (Centaurus A)

We sincerely thank the referee (Erik Rosolowsky) for the careful reading and useful comments to improve our manuscript. We would also like to show our gratitude to him for the kind assistance with the usage of CPROPS in the early stages of this work. REM was supported by the ALMA Japan Research Grant of NAOJ ALMA Project, NAOJ-ALMA-222. DE was supported by JSPS KAKENHI grant number JP 17K14254. DE was supported by the ALMA Japan Research Grant of NAOJ ALMA Project, NAOJ-ALMA-0093. MINK was supported by JSPS KAKENHI grant number JP 15J04974. KK was supported by JSPS KAKENHI grant number JP17H06130 and the NAOJ ALMA Scientific Research grant number 2017-06B. SV acknowledges support by the research projects AYA2014-53506-P and AYA2017-84897-P from the Spanish Ministerio de Economia y Competitividad, and by the Consejer ' ia de Conocimiento, Investigaci ' on y Universidad, Junta de Andaluc ' ia (FQM108) and European Regional Development Fund (ERDF)". This study has been partially financed by the Consejer ' ia de Conocimiento, Investigaci ' on y Universidad, Junta de Andaluc ' ia and European Regional Development Fund (ERDF), ref. SOMM17/6105/UGR. Part of this work was achieved using the grant of Visiting Scholars Program supported by the Research Coordination Committee, National Astronomical Observatory of Japan (NAOJ), National Institutes ofNatural Sciences (NINS). SM would like to thank the Ministry of Science and Technology (MOST) of Taiwan, MOST 107-2119-M-001-020. This research has made use of NASA's Astrophysics Data System. This research has made use of Astropy, a community-developed core PYTHON (http://www.python.org) package for Astronomy (Astropy Collaboration 2013, 2018); IPYTHON (Perez & Granger 2007); MATPLOTLIB (Hunter 2007); APLPY, an open-source plotting package for PYTHON (Robitaille & Bressert 2012), and NUMPY (van derWalt, Colbert & Varoquaux 2011). Data analysis was in part carried out on the open use data analysis computer system at the Astronomy Data Center, ADC, of the National Astronomical Observatory of Japan. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2013.1.00803.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic ofKorea), in cooperationwith theRepublic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The NationalRadio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.We present the first census of giant molecular clouds (GMCs) complete down to 106M and within the inner 4 kpc of the nearest giant elliptical and powerful radio galaxy, Centaurus A. We identified 689 GMCs using CO(1–0) data with 1 arcsec spatial resolution (∼20 pc) and 2 kms−1 velocity resolution obtained with the Atacama Large Millimeter/submillimeter Array. The I(CO)-N(H2) conversion factor based on the virial method is XCO = (2 ± 1) × 1020 cm−2(K km s−1)−1 for the entire molecular disc, consistent with that of the discs of spiral galaxies including the Milky Way, and XCO = (5 ± 2) × 1020 cm−2(K km s−1)−1 for the circumnuclear disc (CND; within a galactocentric radius of 200 pc). We obtained the GMC mass spectrum distribution and find that the best truncated power-law fit for the whole molecular disc, with index γ −2.41 ± 0.02 and upper cut-off mass ∼1.3 × 107M , is also in agreement with that of nearby disc galaxies. A trend is found in the mass spectrum index from steep to shallow as we move to inner radii. Although the GMCs are in an elliptical galaxy, the general GMC properties in the molecular disc are as in spiral galaxies. However, in the CND, large offsets in the line-width-size scaling relations (∼0.3 dex higher than those in the GMCs in the molecular disc), a different XCO factor, and the shallowest GMC mass distribution shape (γ = −1.1 ± 0.2) all suggest that there the GMCs are most strongly affected by the presence of the active galactic nucleus and/or shear motions.ALMA Japan Research Grant of NAOJ ALMA Project NAOJ-ALMA-222 NAOJ-ALMA-0093Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of ScienceGrants-in-Aid for Scientific Research (KAKENHI) JP 17K14254 JP 15J04974 JP17H06130NAOJ ALMA Scientific Research grant 2017-06BSpanish Government AYA2014-53506-P AYA2017-84897-PJunta de Andalucia FQM108European Commission SOMM17/6105/UGRResearch Coordination Committee, National Astronomical Observatory of Japan (NAOJ), National Institutes ofNatural Sciences (NINS)Ministry of Science and Technology, Taiwan MOST 107-2119-M-001-020 2013.1.00803.

The Sloan Digital Sky Survey-II Supernova Survey: Search Algorithm and Follow-up Observations

The Sloan Digital Sky Survey-II Supernova Survey has identified a large number of new transient sources in a 300 sq. deg. region along the celestial equator during its first two seasons of a three-season campaign. Multi-band (ugriz) light curves were measured for most of the sources, which include solar system objects, Galactic variable stars, active galactic nuclei, supernovae (SNe), and other astronomical transients. The imaging survey is augmented by an extensive spectroscopic follow-up program to identify SNe, measure their redshifts, and study the physical conditions of the explosions and their environment through spectroscopic diagnostics. During the survey, light curves are rapidly evaluated to provide an initial photometric type of the SNe, and a selected sample of sources are targeted for spectroscopic observations. In the first two seasons, 476 sources were selected for spectroscopic observations, of which 403 were identified as SNe. For the Type Ia SNe, the main driver for the Survey, our photometric typing and targeting efficiency is 90%. Only 6% of the photometric SN Ia candidates were spectroscopically classified as non-SN Ia instead, and the remaining 4% resulted in low signal-to-noise, unclassified spectra. This paper describes the search algorithm and the software, and the real-time processing of the SDSS imaging data. We also present the details of the supernova candidate selection procedures and strategies for follow-up spectroscopic and imaging observations of the discovered sources.Comment: Accepted for publication in The Astronomical Journal (66 pages, 13 figures); typos correcte

Clusters of Galaxies in the First Half of the Universe from the IRAC Shallow Survey

We have identified 335 galaxy cluster and group candidates, 106 of which are at z > 1, using a 4.5 um selected sample of objects from a 7.25 deg^2 region in the Spitzer Infrared Array Camera (IRAC) Shallow Survey. Clusters were identified as 3-dimensional overdensities using a wavelet algorithm, based on photometric redshift probability distributions derived from IRAC and NOAO Deep Wide-Field Survey data. We estimate only ~10% of the detections are spurious. To date 12 of the z > 1 candidates have been confirmed spectroscopically, at redshifts from 1.06 to 1.41. Velocity dispersions of ~750 km/s for two of these argue for total cluster masses well above 10^14 M_sun, as does the mass estimated from the rest frame near infrared stellar luminosity. Although not selected to contain a red sequence, some evidence for red sequences is present in the spectroscopically confirmed clusters, and brighter galaxies are systematically redder than the mean galaxy color in clusters at all redshifts. The mean I - [3.6] color for cluster galaxies up to z ~ 1 is well matched by a passively evolving model in which stars are formed in a 0.1 Gyr burst starting at redshift z_f = 3. At z > 1, a wider range of formation histories is needed, but higher formation redshifts (i.e. z_f > 3) are favored for most clusters.Comment: 56 pages, 19 figures, 3 tables, landscape tables 1 (p. 14) and 2 (p. 29) should be printed separately. Accepted for publication in Astrophysical Journal, updated version will be posted upon publicatio