- ID:
- ivo://CDS.VizieR/J/PASJ/57/165
- Title:
- Ly{alpha} emitters in the SUBARU Deep Field
- Short Name:
- J/PASJ/57/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new results of a deep optical imaging survey using a narrow band filter (NB921) centered at {lambda}=9196{AA} together with B, V, R, i', and z' broadband filters in the sky area of the Subaru Deep Field, which has been promoted as one of legacy programs of the 8.2m Subaru Telescope. We obtained a photometric sample of 58 Ly{alpha} emitter candidates at z~6.5-6.6 among ~180 strong NB921-excess (z'-NB921>1.0) objects together with a color criterion of i'-z'>1.3. We then obtained optical spectra of 20 objects in our NB921-excess sample, and identified at least nine Ly{alpha} emitters at z~6.5-6.6, including the two emitters reported by Kodaira et al. (2003PASJ...55L..17K). Since our Ly{alpha}-emitter candidates are free from strong amplification of gravitational lensing, we are able to discuss their observational properties from a statistical point of view. Based on these new results, we obtained a lower limit of the star-formation rate density of rho_SFR_~5.7x10^-4^h_0.7_M_{sun}/yr/Mpc^3^ at z~6.6, being consistent with our previous estimate. We discuss the nature of star-formation activity in galaxies beyond z=6.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/L54
- Title:
- Ly{alpha} emitters (LAE) in A1689-7.1
- Short Name:
- J/MNRAS/403/L54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of a large-scale structure of emission-line galaxies at redshift z=4.86 behind a massive cluster of galaxies, A1689. Previous spectroscopic observations of a galaxy, A1689-7.1 at z=4.87, near this structure, revealed a possible overdense region of intergalactic medium (IGM) around the galaxy, which extends at least ~80 comoving Mpc along the line of sight. In order to investigate whether this z~5 IGM overdense region contains a galaxy overdensity, we undertook narrow- and broad-band imaging observations around A1689-7.1 with Subaru/Suprime-Cam. We detected 51 candidates as Ly{alpha} emitters at redshift z=4.86+/-0.03 in the 32x24-arcmin^2^ field of view. After correction for lensing by the foreground cluster, we found a large-scale (~20x60 comoving Mpc) overdense region of galaxies around A1689-7.1 in the source plane at z=4.86. The densest peak in this region has an overdensity of {delta}~4, suggesting that this structure is probably a good candidate for a protocluster which may evolve into a massive cluster of galaxies in the present-day Universe. A1689-7.1 is located at the edge of this region, where the local galaxy density is ~1.6 times the mean density and is close to the density contrast in the IGM along the line of sight to A1689-7.1 estimated from the optical depth. The overdensities of galaxies we have found may suggest that at least some parts of the IGM overdense region have already started to form galaxies and moreover they relate to the formation of a protocluster. Although we lack information on the three-dimensional distributions of both IGM and galaxy overdense regions, the similarity of the scales of both regions may suggest that the two are parts of a single large-scale structure, which would be an large edge-on sheet along the line of sight with a size of ~20x60x80 comoving Mpc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/L66
- Title:
- Ly{alpha} emitters near B3 J2330+3927
- Short Name:
- J/MNRAS/400/L66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of a candidate of giant radio-quiet Ly{alpha} blob (RQLAB) in a large-scale structure around a high-redshift radio galaxy (HzRG) lying in a giant Ly{alpha} halo B3 J2330+3927 at redshift z=3.087. We obtained narrow- and broad-band imaging around B3 J2330+3927 with Subaru/Suprime-Cam to search for Ly{alpha} emitters (LAEs) and absorbers (LAAs) at redshift z=3.09+/-0.03. We detected candidate 127 LAEs and 26 LAAs in the field of view of 31x24arcmin^2^ (58x44 comoving Mpc).
- ID:
- ivo://CDS.VizieR/J/ApJ/680/1072
- Title:
- Ly{alpha}-emitting galaxies at 0.2<z<0.35
- Short Name:
- J/ApJ/680/1072
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the GALEX (Galaxy Evolution Explorer) spectroscopic survey mode, with a resolution of ~8{AA} in the far-ultraviolet (FUV; 1350-1750{AA}) and ~20{AA} in the near-ultraviolet (NUV; 1950-2750{AA}) for a systematic search of Ly{alpha}-emitting galaxies at low redshift. Our aim is to fill a gap between high-redshift surveys and a small set of objects studied in detail in the nearby universe. A blind search of 7018 spectra extracted in five deep exposures (5.65deg^2^) has resulted in 96 Ly{alpha}-emitting galaxy candidates in the FUV domain after accounting for broad-line AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/671/1227
- Title:
- Ly{alpha} galaxies at z~4.5
- Short Name:
- J/ApJ/671/1227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 59 z~4.5 Ly{alpha}-emitting galaxies spectroscopically confirmed in a campaign of Keck DEIMOS follow-up observations to candidates selected in the Large Area Ly{alpha} (LALA) narrowband imaging survey. We targeted 97 candidates for spectroscopic follow-up; by accounting for the variety of conditions under which we performed spectroscopy, we estimate a selection reliability of ~76%. Together with our previous sample of Keck LRIS confirmations, the 59 sources confirmed herein bring the total catalog to 73 spectroscopically confirmed z~4.5 Ly{alpha}-emitting galaxies in the ~0.7deg^2^ covered by the LALA imaging.
- ID:
- ivo://CDS.VizieR/J/ApJ/844/171
- Title:
- Ly{alpha} profile in 43 Green Pea galaxies
- Short Name:
- J/ApJ/844/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied Lyman-{alpha} (Ly{alpha}) escape in a statistical sample of 43 Green Peas with HST/COS Ly{alpha} spectra. Green Peas are nearby star-forming galaxies with strong [OIII]{lambda}5007 emission lines. Our sample is four times larger than the previous sample and covers a much more complete range of Green Pea properties. We found that about two-thirds of Green Peas are strong Ly{alpha} line emitters with rest-frame Ly{alpha} equivalent width >20{AA}. The Ly{alpha} profiles of Green Peas are diverse. The Ly{alpha} escape fraction, defined as the ratio of observed Ly{alpha} flux to intrinsic Ly{alpha} flux, shows anti-correlations with a few Ly{alpha} kinematic features-both the blue peak and red peak velocities, the peak separations, and the FWHM of the red portion of the Ly{alpha} profile. Using properties measured from Sloan Digital Sky Survey optical spectra, we found many correlations-the Ly{alpha} escape fraction generally increases at lower dust reddening, lower metallicity, lower stellar mass, and higher [OIII]/[OII] ratio. We fit their Ly{alpha} profiles with the HI shell radiative transfer model and found that the Ly{alpha} escape fraction is anti-correlated with the best-fit N_HI_. Finally, we fit an empirical linear relation to predict f_esc_^Ly{alpha}^ from the dust extinction and Ly{alpha} red peak velocity. The standard deviation of this relation is about 0.3dex. This relation can be used to isolate the effect of intergalactic medium (IGM) scatterings from Ly{alpha} escape and to probe the IGM optical depth along the line of sight of each z>7 Ly{alpha} emission-line galaxy in the James Webb Space Telescope era.
- ID:
- ivo://CDS.VizieR/J/MNRAS/504/3662
- Title:
- Lya-UV Offsets in Galaxies at z~6
- Short Name:
- J/MNRAS/504/3662
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We study the projected spatial offset between the ultraviolet continuum and Lya emission for 65 lensed and unlensed galaxies in the Epoch of Reionization 5<=z<=7, the first such study at these redshifts, in order to understand the potential for these offsets to confuse estimates of the Lya properties of galaxies observed in slit spectroscopy. While we find that ~40% of galaxies in our sample show significant projected spatial offsets, |Delta_Lya-UV_|, we find a relatively modest average (median) projected offset of |Delta_Lya-UV_|=0.61+/-0.08 proper kpc for the entire sample. A small fraction of our sample, ~10%, exhibit offsets in excess of 2 proper kpc, with offsets seen up to ~4 proper kpc, sizes that are considerably larger than the effective radii of typical galaxies at these redshifts. An internal comparison and a comparison to studies at lower redshift yielded no significant evidence of evolution of Delta_Lya-UV with redshift. In our sample, UV-bright galaxies (with a median L_UV_/L*_UV_=0.67) showed offsets a factor of three greater than their fainter counterparts (median L_UV_/L*_UV_=0.10), 0.89 +/-0.18 vs. 0.27+/-0.05 proper kpc, respectively. The presence of companion galaxies and early-stage merging activity appeared to be unlikely causes of these offsets. Rather, these offsets appear consistent with a scenario in which internal anisotropic processes resulting from stellar feedback, which is stronger in UV-brighter galaxies, facilitate Lya fluorescence and/or backscattering from nearby or outflowing gas. The reduction in the Lya flux due to offsets was quantified. It was found that the differential loss of Lya photons for galaxies with average offsets is not, if corrected for, a limiting factor for all but the narrowest slit widths (<0.4"). However, for the largest offsets, if they are mostly perpendicular to the slit major axis, slit losses were found to be extremely severe in cases where slit widths of <=1" were employed, such as those planned for James Webb Space Telescope/NIRSpec observations.
- ID:
- ivo://CDS.VizieR/J/A+A/498/13
- Title:
- Lyman-{alpha} emitters from redshifts z~2-3
- Short Name:
- J/A+A/498/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Narrow-band surveys to detect Ly{alpha} emitters are powerful tools for identifying high, and very high, redshift galaxies. Although samples are increasing at redshifts z=3-6, the nature of these galaxies is still poorly known. The number of galaxies detected at redshifts below z~3 are also small. We study the properties of z=2.25 Ly{alpha} emitters and compare them with those of z>3 Ly{alpha} emitters We present narrow-band imaging made with the MPG/ESO 2.2m telescope and the WFI (Wide Field Imager) detector. Using this data, we have searched for emission-line objects. We find 170 candidate typical Ly{alpha} emitters and 17 candidates that we regard as high UV-transmission Ly{alpha} emitters. We have derived the magnitudes of these objects in 8 photometric bands from u* to K_s_, and studied whether they have X-ray and/or radio counterparts.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/11
- Title:
- Magellan/IMACS spectra of Crater II & Hercules
- Short Name:
- J/ApJ/883/11
- Date:
- 21 Jan 2022 09:25:05
- Publisher:
- CDS
- Description:
- We investigate the possibility that the dwarf galaxies Crater II and Hercules have previously been tidally stripped by the Milky Way. We present Magellan/IMACS spectra of candidate member stars in both objects. We identify 37 members of Crater II, 25 of which have velocity measurements in the literature, and we classify three stars within that subset as possible binaries. We find that including or removing these binary candidates does not change the derived velocity dispersion of Crater II. Excluding the binary candidates, we measure a velocity dispersion of {sigma}_Vlos_=2.7_-0.4_^+0.5^km/s, corresponding to M/L=47_-13_^+17^M_{sun}_/L_{sun}_. We measure a mean metallicity of [Fe/H]=-1.95_-0.05_^+0.06^, with a dispersion of {sigma}_[Fe/H]_=0.18_-0.08_^+0.06^. Our velocity dispersion and metallicity measurements agree with previous measurements for Crater II, and confirm that the galaxy resides in a kinematically cold dark-matter halo. We also search for spectroscopic members stripped from Hercules in the possible extratidal stellar overdensities surrounding the dwarf. For both galaxies, we calculate proper motions using Gaia DR2 astrometry, and use their full 6D phase space information to evaluate the probability that their orbits approach sufficiently close to the Milky Way to experience tidal stripping. Given the available kinematic data, we find a probability of ~40% that Hercules has suffered tidal stripping. The proper motion of Crater II makes it almost certain to be stripped.
- ID:
- ivo://CDS.VizieR/J/ApJ/779/87
- Title:
- MAGIICAT. III. Virial masses
- Short Name:
- J/ApJ/779/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In Churchill et al. (2013ApJ...763L..42C), we used halo abundance matching applied to 182 galaxies in the MgII Absorber-Galaxy Catalog (MAGIICAT) and showed that the mean MgII{lambda}2796 equivalent width follows a tight inverse-square power law, W_r_(2796){prop.to}(D/R_vir_)^-2^, with projected location relative to the galaxy virial radius and that the MgII absorption covering fraction is effectively invariant with galaxy virial mass, M_h_, over the range 10.7<=logM_h_/M_{sun}_<=13.9. In this work, we explore multivariate relationships between W_r_(2796), virial mass, impact parameter, virial radius, and the theoretical cooling radius that further elucidate self-similarity in the cool/warm (T=10^4^-10^4.5^K) circumgalactic medium (CGM) with virial mass. We show that virial mass determines the extent and strength of the MgII absorbing gas such that the mean W_r_(2796) increases with virial mass at fixed distance while decreasing with galactocentric distance for fixed virial mass. The majority of the absorbing gas resides within D=~0.3R_vir_, independent of both virial mass and minimum absorption threshold; inside this region, and perhaps also in the region 0.3<D/R_vir_<=1, the mean W_r_(2796) is independent of virial mass. Contrary to absorber-galaxy cross-correlation studies, we show there is no anti-correlation between W_r_(2796) and virial mass. We discuss how simulations and theory constrained by observations support self-similarity of the cool/warm CGM via the physics governing star formation, gas-phase metal enrichment, recycling efficiency of galactic scale winds, filament and merger accretion, and overdensity of local environment as a function of virial mass.
