V, R, and I CCD images are used to investigate the photometric properties and spatial distribution of supergiants in the nearby interacting galaxy NGC 672. Not counting stars imbedded in H II regions, our sample consists of 237 objects. The (V-R,V-I) two-color diagram indicates that the majority of these stars have spectral types between A-K. Statistical tests show that the outer region of NGC 672 contains a redder population of supergiants than the inner region. Comparisons with theoretical evolutionary tracks indicate that the majority of the supergiants in NGC 672 have progenitor masses between 15M_{sun}_ and 25M_{sun}_, and that the inner regions contain stars that are more massive than in the outer disk, indicating that an age gradient is present. The luminosity functions in all three bandpasses follow power laws, and the exponent in V=0.79+/-0.06, in good agreement with other galaxies. The brightest red supergiants occur at V~22.0, from which we derive a distance modulus of 29.5, corresponding to 7.9(+1.0)(-0.9)Mpc.
We analyze the >4{sigma} sources in the most sensitive 100arcmin^2^ area (rms<0.56mJy) of a SCUBA-2 850{mu}m survey of the GOODS-S and present the 75 band-7 ALMA sources (>4.5{sigma}) obtained from high-resolution interferometric follow-up observations. The raw SCUBA-2 >4{sigma} limit is fainter than 2.25mJy throughout this region, and deboosting corrections would lower this further. Of the 53 SCUBA-2 sources in this sample, only five have no ALMA detections, while 13% (68% confidence range 7%-19%) have multiple ALMA counterparts. Color-based high-redshift dusty galaxy selection techniques find at most 55% of the total ALMA sample. In addition to using literature spectroscopic and optical/near-infrared photometric redshifts, we estimate far infrared photometric redshifts based on an Arp 220 template. We identify seven z>~4 candidates. We see the expected decline with redshift of the 4.5 and 24{mu}m to 850{mu}m flux ratios, confirming these as good diagnostics of z>~4 candidates. We visually classify 52 ALMA sources, finding 44% (68% confidence range 35%-53%) to be apparent mergers. We calculate rest-frame 2-8keV and 8-28keV luminosities using the 7Ms Chandra X-ray image. Nearly all of the ALMA sources detected at 0.5-2keV are consistent with a known X-ray luminosity to 850{mu}m flux relation for star-forming galaxies, while most of those detected at 2-7keV are moderate-luminosity AGNs that lie just above the 2-7keV detection threshold. The latter largely have substantial obscurations of logN_H_=23-24cm^-2^, but two of the high-redshift candidates may even be Compton thick.
In this first paper in the SUPER GOODS series on powerfully star-forming galaxies in the two GOODS fields, we present a deep SCUBA-2 survey of the GOODS-N at both 850 and 450{mu}m (central rms noise of 0.28mJy and 2.6mJy, respectively). In the central region, the 850{mu}m observations cover the GOODS-N to near the confusion limit of ~1.65mJy, while over a wider 450arcmin^2^ region-well complemented by Herschel far-infrared imaging-they have a median 4{sigma} limit of 3.5mJy. We present >=4{sigma} catalogs of 186 850{mu}m and 31 450{mu}m selected sources. We use interferometric observations from the Submillimeter Array (SMA) and the Karl G. Jansky Very Large Array (VLA) to obtain precise positions for 114 SCUBA-2 sources (28 from the SMA, all of which are also VLA sources). We present new spectroscopic redshifts and include all existing spectroscopic or photometric redshifts. We also compare redshifts estimated using the 20cm/850{mu}m and the 250cm/850{mu}m flux ratios. We show that the redshift distribution increases with increasing flux, and we parameterize the dependence. We compute the star formation history and the star formation rate (SFR) density distribution functions in various redshift intervals, finding that they reach a peak at z=2-3 before dropping to higher redshifts. We show that the number density per unit volume of SFR>~500M_{sun}_/yr galaxies measured from the SCUBA-2 sample does not change much relative to that of lower SFR galaxies from UV selected samples over z=2-5, suggesting that, apart from changes in the normalization, the shape in the number density as a function of SFR is invariant over this redshift interval.
The Chandra Deep Field (CDF)-S is the deepest X-ray image available and will remain so for the near future. We provide a spectroscopic (64.5%; 64% with spectral classifications) and photometric redshift catalog for the full 7Ms sample, but much of our analysis focuses on the central (off-axis angles <5.7') region, which contains a large, faint ALMA sample of 75 >4.5{sigma} 850{mu}m sources. We measure the 850{mu}m fluxes at the X-ray positions using the ALMA images, where available, or an ultradeep SCUBA-2 map. We find that the full X-ray sample produces ~10% of the 850{mu}m extragalactic background light. We separate the submillimeter-detected X-ray sources into star-forming galaxies and active galactic nuclei (AGNs) using a star formation rate (SFR) versus X-ray luminosity calibration for high-SFR galaxies. We confirm this separation using the X-ray photon indices. We measure the X-ray fluxes at the accurate positions of the 75 ALMA sources and detect 70% at >3{sigma} in either the 0.5-2 or 2-7keV bands. However, many of these may produce both their X-ray and submillimeter emission by star formation. Indeed, we find that only 20% of the ALMA sources have intermediate X-ray luminosities (rest-frame 8-28 keV luminosities of 10^42.5^-10^44^erg/s), and none has a high X-ray luminosity (>10^44^erg/s). Conversely, after combining the CDF-S with the CDF-N, we find extreme star formation (SFR>300M_{sun}_/yr) in some intermediate X-ray luminosity sources but not in any high X-ray luminosity sources. We argue that the quenching of star formation in the most luminous AGNs may be a consequence of the clearing of gas in these sources.
The Pan-STARRS1 (PS1) survey has obtained imaging in five bands (griz y_P1_) over 10 Medium Deep Survey (MDS) fields covering a total of 70 square degrees. This paper describes the search for apparently hostless supernovae (SNe) within the first year of PS1 MDS data with an aim of discovering superluminous supernovae (SLSNe). A total of 249 hostless transients were discovered down to a limiting magnitude of M_AB_~23.5, of which 76 were classified as Type Ia supernovae (SNe Ia). There were 57 SNe with complete light curves that are likely core-collapse SNe (CCSNe) or type Ic SLSNe and 12 of these have had spectra taken. Of these 12 hostless, non-Type Ia SNe, 7 were SLSNe of type Ic at redshifts between 0.5 and 1.4. This illustrates that the discovery rate of type Ic SLSNe can be maximized by concentrating on hostless transients and removing normal SNe Ia. We present data for two possible SLSNe; PS1-10pm (z=1.206) and PS1-10ahf (z=1.1), and estimate the rate of type Ic SLSNe to be between 3^+3^_-2_x10^-5^ and 8^+2^_-1_x10^-5^ that of the CCSN rate within 0.3<=z<=1.4 by applying a Monte Carlo technique. The rate of slowly evolving, type Ic SLSNe (such as SN2007bi) is estimated as a factor of 10 lower than this range.
We present optical photometry and spectroscopy of the Type II supernova ASASSN-14jb, together with very large telescope (VLT) multi unit spectroscopic explorer (MUSE) integral field observations of its host galaxy and a nebular-phase spectrum. This supernova, in the nearby galaxy ESO 467-G051 (z=0.006), was discovered and followed-up by the all-sky automated survey for supernovae (ASAS-SN). We obtained well-sampled las cumbres network (LCOGTN) BVgri and Swift w2m1w1ubv optical, near-UV/optical light curves, and several optical spectra in the early photospheric phases. The transient ASASSN-14jb exploded ~2kpc above the star-forming disk of ESO 467-G051, an edge-on disk galaxy. The large projected distance from the disk of the supernova position and the non-detection of any HII region in a 1.4kpc radius in projection are in conflict with the standard environment of core-collapse supernova progenitors and suggests the possible scenario that the progenitor received a kick in a binary interaction. We present analysis of the optical light curves and spectra, from which we derived a distance of 25+/-2Mpc using state-of-the-art empirical methods for Type II SNe, physical properties of the SN explosion (^56^Ni mass, explosion energy, and ejected mass), and properties of the progenitor; namely the progenitor radius, mass, and metallicity. Our analysis yields a ^56^Ni mass of 0.0210+/-0.0025M_{sun}_, an explosion energy of ~0.25x10^51^ergs, and an ejected mass of ~6M_{sun}_. We also constrained the progenitor radius to be R*=580+/-28R_{sun}_ which seems to be consistent with the sub-Solar metallicity of 0.3+/-0.1Z_{sun}_ derived from the supernova FeII {lambda} 5018 line. The nebular spectrum constrains strongly the progenitor mass to be in the range 10-12M_{sun}_. From the Spitzer data archive we detect ASASSN-14jb ~330-days past explosion and we derived a total dust mass of 10^-4^M_{sun}_ from the 3.6um and 4.5um photometry. Using the FUV, NUV, BVgri,Ks, 3.6um, and 4.5u total magnitudes for the host galaxy, we fit stellar population synthesis models, which give an estimate of M*~1x10^9^M_{sun}_ , an age of 3.2Gyr, and a SFR~0.07M_{sun}_/yr. We also discuss the low oxygen abundance of the host galaxy derived from the MUSE data, having an average of 12+log(O/H)=8.27^+0.16^_-0.20_ using the O3N2 diagnostic with strong line methods. We compared it with the supernova spectra, which is also consistent with a sub-Solar metallicity progenitor. Following recent observations of extraplanar H II regions in nearby edge-on galaxies, we derived the metallicity offset from the disk, being positive, but consistent with zero at 2{sigma}, suggesting enrichment from disk outflows. We finally discuss the possible scenarios for the unusual environment for ASASSN-14jb and conclude that either the in-situ star formation or runaway scenario would imply a low-mass progenitor, agreeing with our estimate from the supernova nebular spectrum. Regardless of the true origin of ASASSN-14jb, we show that the detailed study of the environment roughly agree with the stronger constraints from the observation of the transient.
We report the creation of large and well-defined database that combines extensive new measurements and a literature search of 3876 supernovae (SNe) and their 3679 host galaxies located in the sky area covered by the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8). This database should be much larger than previous ones, and should contain a homogenous set of global parameters of SN hosts, including morphological classifications and measures of nuclear activity. Identification of the host galaxy sample is 91% complete (with 3536 SNe in 3340 hosts), of which the SDSS names of ~1100 anonymous hosts are listed for the first time. The morphological classification is available for 2104 host galaxies, including 73 (56) hosts in interacting (merging) systems. The total sample of host galaxies collects heliocentric redshifts for 3317 (~90%) galaxies. The g-band magnitudes, D_25_, b/a, and PA are available for 2030 hosts of the morphologically classified sample of galaxies. Nuclear activity measures are provided for 1189 host galaxies. We analyze and discuss many selection effects and biases that can significantly affect any future analysis of our sample. The creation of this large database will help to better understand how the different types of SNe are correlated with the properties of the nuclei and global physical parameters of the host galaxies, and minimize possible selection effects and errors that often arise when data are selected from different sources and catalogues.
Large samples of high-redshift supernovae (SNe) are potentially powerful probes of cosmic star formation, metal enrichment and SN physics. We present initial results from a new deep SN survey, based on re-imaging in the R, i', z' bands, of the 0.25deg^2^ Subaru Deep Field (SDF), with the 8.2-m Subaru telescope and Suprime-Cam. In a single new epoch consisting of two nights of observations, we have discovered 33 candidate SNe, down to a z'-band magnitude of 26.3 (AB). We have measured the photometric redshifts of the SN host galaxies, obtained Keck spectroscopic redshifts for 17 of the host galaxies and classified the SNe using the Bayesian photometric algorithm of Poznanski et al. (2007AJ....134.1285P) that relies on template matching.
The Type Ia supernova (SN Ia) rate, when compared to the cosmic star formation history (SFH), can be used to derive the delay-time distribution (DTD; the hypothetical SN Ia rate versus time following a brief burst of star formation) of SNe Ia, which can distinguish among progenitor models. We present the results of a supernova (SN) survey in the Subaru Deep Field (SDF). Over a period of 3 years, we have observed the SDF on four independent epochs with Suprime-Cam on the Subaru 8.2-m telescope, with two nights of exposure per epoch, in the R, i' and z' bands. We have discovered 150 SNe out to redshift z~=2. Using 11 photometric bands from the observer-frame far-ultraviolet to the near-infrared, we derive photometric redshifts for the SN host galaxies (for 24 we also have spectroscopic redshifts). This information is combined with the SN photometry to determine the type and redshift distribution of the SN sample. Our final sample includes 28 SNe Ia in the range 1.0<z<1.5 and 10 in the range 1.5<z<2.0.
Stripped-envelope supernovae (SE SNe) of Type Ib and Type Ic are thought to result from explosions of massive stars having lost their outer envelopes. The favoured explosion mechanism is by core-collapse, with the shock later revived by neutrino heating. However, there is an upper limit to the amount of radioactive ^56^Ni that such models can accomplish. Recent literature point to a tension between the maximum luminosity from such simulations and observations. We use a well characterized sample of SE SNe from the Zwicky Transient Facility (ZTF) Bright Transient Survey (BTS). We scrutinize the observational caveats regarding estimating the maximum luminosity (and thus the amount of ejected radioactive nickel) for the members of this sample. We employ the strict selection criteria for the BTS to collect a sample of spectroscopically classified normal Type Ibc SNe for which we use the ZTF light curves to determine the maximum luminosity. We cull the sample further based on data quality, light-curve shape, distance and colors, and examine uncertainties that may affect the numbers. The methodology of the sample construction from this BTS sample can be used for many other future investigations. We analyze observational data, consisting of optical light curves and spectra, for the selected sub-samples. In total we use 129 Type Ib or Type Ic BTS SNe with an initial rough luminosity distribution peaked at M_r_=-17.61+/-0.72, and where 36% are apparently brighter than the theoretically predicted maximum brightness of M_r_=-17.8. When we further cull this sample to ensure that the SNe are normal Type Ibc with good LC data within the Hubble flow, the sample of 94 objects has M_r_=-17.64+/-0.54. A main uncertainty in absolute magnitude determinations for SNe is the host galaxy extinction correction, but the reddened objects only get more luminous after corrections. If we simply exclude objects with red, unusual or uncertain colors, we are left with 14 objects at M_r_=-17.90+/-0.73, whereof a handful are most certainly brighter than the suggested theoretical limit. The main result of this study is thus that normal SNe Ibc do indeed reach luminosities above 10^42.6^erg/s, apparently in conflict with existing explosion models.
