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Register a new userA 16 deg$^2$ survey of emission-line galaxies at z<1.5 in HSC-SSP PDR1
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We present initial results from the Subaru Strategic Program (SSP) with Hyper Suprime-Cam (HSC) on a comprehensive survey of emission-line galaxies at z<1.5 based on narrowband (NB) imaging. The first Public Data Release (PDR1) provides us with data from two NB filters, specifically NB816 and NB921 over 5.7 deg$^2$ and 16.2 deg$^2$ respectively. The $5 sigma$ limiting magnitudes are 25.2 (UDeep layer, 1.4 deg$^2$) and 24.8 (Deep layer, 4.3 deg$^2$) mag in NB816, and 25.1 (UDeep, 2.9 deg$^2$) and 24.6--24.8 (Deep, 13.3 deg$^2$) mag in NB921. The wide-field imaging allows us to construct unprecedentedly large samples of 8,054 H$alpha$ emitters at z ~ 0.25 and 0.40, 8,656 [OIII] emitters at z ~ 0.63 and 0.84, and 16,877 [OII] emitters at z ~ 1.19 and 1.47. We map the cosmic web on scales out to about 50 comoving Mpc that includes galaxy clusters, identified by red sequence galaxies, located at the intersection of filamentary structures of star-forming galaxies. The luminosity functions of emission-line galaxies are measured with precision and consistent with published studies. The wide field coverage of the data enables us to measure the luminosity functions up to brighter luminosities than previous studies. The comparison of the luminosity functions between the different HSC-SSP fields suggests that a survey volume of $>5times10^5$ Mpc$^3$ is essential to overcome cosmic variance. Since the current data have not reached the full depth expected for the HSC-SSP, the color cut in i-NB816 or z-NB921 induces a bias towards star-forming galaxies with large equivalent widths, primarily seen in the stellar mass functions for the H$alpha$ emitters at z ~ 0.25--0.40. Even so, the emission-line galaxies clearly cover a wide range of luminosity, stellar mass, and environment, thus demonstrating the usefulness of the NB data from the HSC-SSP to investigate star-forming galaxies at z<1.5.
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We have conducted a comprehensive survey of emission-line galaxies at $zlesssim1.6$ based on narrowband (NB) imaging data taken with Hyper Suprime-Cam (HSC) on the Subaru telescope. In this paper, we update the catalogs of H$alpha$, [OIII], and [OII] emission-line galaxies using the data from the second Public Data Release (PDR2) of Subaru Strategic Program (SSP) of HSC and Cosmic HydrOgen Reionization Unveiled with Subaru (CHORUS) survey along with the spectroscopic redshifts for 2,019 emission-line galaxies selected with the PDR1 data. The wider effective coverage of NB816 and NB921, 16.3 deg$^2$ and 16.9 deg$^2$ respectively, are available in the Deep and UltraDeep layers of HSC-SSP from the PDR2. The CHORUS survey provides us with data with additional three NBs (NB527, NB718, and NB973) in the COSMOS field in the UltraDeep layer (1.37 deg$^2$). The five NB datasets allow us to investigate the star-forming galaxies presenting emission-lines at 14 specific redshifts ranging from $zsim1.6$ down to $zsim0.05$. We revisit the distribution of large-scale structures and luminosity functions (LFs) for the emission-line galaxies with the large samples of 75,377 emission-line galaxies selected. The redshift revolution of LFs shows that the star formation rate densities (SFRDs) decreases monotonically from $zsim1.6$, which is consistent with the cosmic SFRD ever known. Our samples of emission-line galaxies covering a sufficiently large survey volume are useful to investigate the evolution of star-forming galaxies since the cosmic noon in a wide range of environments including galaxy clusters, filaments, and voids.
We compare the physical and morphological properties of z ~ 2 Lyman-alpha emitting galaxies (LAEs) identified in the HETDEX Pilot Survey and narrow band studies with those of z ~ 2 optical emission line galaxies (oELGs) identified via HST WFC3 infrared grism spectroscopy. Both sets of galaxies extend over the same range in stellar mass (7.5 < logM < 10.5), size (0.5 < R < 3.0 kpc), and star-formation rate (~1 < SFR < 100). Remarkably, a comparison of the most commonly used physical and morphological parameters -- stellar mass, half-light radius, UV slope, star formation rate, ellipticity, nearest neighbor distance, star formation surface density, specific star formation rate, [O III] luminosity, and [O III] equivalent width -- reveals no statistically significant differences between the populations. This suggests that the processes and conditions which regulate the escape of Ly-alpha from a z ~ 2 star-forming galaxy do not depend on these quantities. In particular, the lack of dependence on the UV slope suggests that Ly-alpha emission is not being significantly modulated by diffuse dust in the interstellar medium. We develop a simple model of Ly-alpha emission that connects LAEs to all high-redshift star forming galaxies where the escape of Ly-alpha depends on the sightline through the galaxy. Using this model, we find that mean solid angle for Ly-alpha escape is 2.4+/-0.8 steradians; this value is consistent with those calculated from other studies.
We present Herschel-PACS spectroscopy of four main-sequence star-forming galaxies at z~1.5. We detect [OI]63micron line emission in BzK-21000 at z=1.5213, and measure a line luminosity, L([OI]63micron) = (3.9+/-0.7)x1.E+9 Lsun. Our PDR modelling of the interstellar medium in BzK-21000 suggests a UV radiation field strength, G~320 G0, and gas density, n~1800 cm-3, consistent with previous LVG modelling of the molecular CO line excitation. The other three targets in our sample are individually undetected in these data, and we perform a spectral stacking analysis which yields a detection of their average emission and an [OI]63micron line luminosity, L([OI]63micron) =(1.1+/-0.2)x1E+9 Lsun. We find that the implied luminosity ratio, L([OI]63micron)/L(IR), of the undetected BzK-selected star-forming galaxies broadly agrees with that of low-redshift star-forming galaxies, while BzK-21000 has a similar ratio to that of a dusty star-forming galaxy at z~6. The high [OI]63micron line luminosities observed in BzK-21000 and the $z sim 1 -3$ dusty and submm luminous star-forming galaxies may be associated with extended reservoirs of low density, cool neutral gas.
We present results from the largest contiguous narrow-band survey in the near-infrared. We have used WIRCam/CFHT and the lowOH2 filter (1.187$pm$0.005 $mu$m) to survey ~10 deg$^2$ of contiguous extragalactic sky in the SA22 field. A total of ~6000 candidate emission-line galaxies are found. We use deep ugrizJK data to obtain robust photometric redshifts. We combine our data with the High-redshift Emission Line Survey (HiZELS), explore spectroscopic surveys (VVDS, VIPERS) and obtain our own spectroscopic follow-up with KMOS, FMOS and MOSFIRE to derive large samples of high-redshift emission-line selected galaxies: 3471 H$alpha$ emitters at z=0.8, 1343 [OIII]+H$beta$ emitters at z=1.4 and 572 [OII] emitters at z=2.2. We probe co-moving volumes of >10$^6$ Mpc$^3$ and find significant over-densities, including an 8.5$sigma$ (spectroscopically confirmed) over-density of H$alpha$ emitters at z=0.81. We derive H$alpha$, [OIII]+H$beta$ and [OII] luminosity functions at z=0.8,1.4,2.2, respectively, and present implications for future surveys such as Euclid. Our uniquely large volumes/areas allow us to sub-divide the samples in thousands of randomised combinations of areas and provide a robust empirical measurement of sample/cosmic variance. We show that surveys for star-forming/emission-line galaxies at a depth similar to ours can only overcome cosmic-variance (errors <10%) if they are based on volumes >5x10$^{5}$ Mpc$^{3}$; errors on $L^*$ and $phi^*$ due to sample (cosmic) variance on surveys probing ~10$^4$ Mpc$^{3}$ and ~10$^5$ Mpc$^{3}$ are typically very high: ~300% and ~40-60%, respectively.
We observed star-forming galaxies at z~1.5 selected from the HyperSuprimeCam Subaru Strategic Program. The galaxies are part of two significant overdensities of [OII] emitters identified via narrow-band imaging and photometric redshifts from grizy photometry. We used VLT/KMOS to carry out Halpha integral field spectroscopy of 46 galaxies in total. Ionized gas maps, star formation rates and velocity fields were derived from the Halpha emission line. We quantified morphological and kinematical asymmetries to test for potential gravitational (e.g. galaxy-galaxy) or hydrodynamical (e.g. ram-pressure) interactions. Halpha emission was detected in 36 targets. 34 of the galaxies are members of two (proto-)clusters at z=1.47, confirming our selection strategy to be highly efficient. By fitting model velocity fields to the observed ones, we determined the intrinsic maximum rotation velocity Vmax of 14 galaxies. Utilizing the luminosity-velocity (Tully-Fisher) relation, we find that these galaxies are more luminous than their local counterparts of similar mass by up to ~4 mag in the rest-frame B-band. In contrast to field galaxies at z<1, the offsets of the z~1.5 (proto-)cluster galaxies from the local Tully-Fisher relation are not correlated with their star formation rates but with the ratio between Vmax and gas velocity dispersion sigma_g. This probably reflects that, as is observed in the field at similar redshifts, fewer disks have settled to purely rotational kinematics and high Vmax/sigma_g ratios. Due to relatively low galaxy velocity dispersions (sigma_v < 400 km/s) of the (proto-)clusters, gravitational interactions likely are more efficient, resulting in higher kinematical asymmetries, than in present-day clusters. (abbr.)
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