- ID:
- ivo://CDS.VizieR/J/ApJ/888/89
- Title:
- Lya galaxies in 3 CFHTLS overdense regions
- Short Name:
- J/ApJ/888/89
- Date:
- 25 Oct 2021 10:16:31
- Publisher:
- CDS
- Description:
- We have carried out follow-up spectroscopy on three overdense regions of g- and r-dropout galaxies in the Canada-France-Hawaii Telescope Legacy Survey Deep Fields, finding two new protoclusters at z=4.898 and 3.721 and a possible protocluster at z=3.834. The z=3.721 protocluster overlaps with a previously identified protocluster at z=3.675. The redshift separation between these two protoclusters is {Delta}z=0.05, which is slightly larger than the size of typical protoclusters. Therefore, if they are not the progenitors of a >10^15^M_{sun}_ halo, they would grow into closely located independent halos like a supercluster. The other protocluster at z=4.898 is also surrounded by smaller galaxy groups. These systems including protoclusters and neighboring groups are regarded as the early phase of superclusters. We quantify the spatial distribution of member galaxies of the protoclusters at z=3.675 and 3.721 by fitting triaxial ellipsoids, finding a tentative difference: one has a pancake-like shape, while the other is filamentary. This could indicate that these two protoclusters are in different stages of formation. We investigate the relation between redshift and the velocity dispersion of protoclusters, including other protoclusters from the literature, in order to compare their dynamical states. Although there is no significant systematic trend in the velocity dispersions of protoclusters with redshift, the distribution is skewed to higher velocity dispersion over the redshift range of z=2-6. This could be interpreted as two phases of cluster formation, one dominated by the steady accretion of galaxies and the other by the merging between group-size halos, perhaps depending on the surrounding large-scale environments.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/740/91
- Title:
- Ly{alpha} and OVI in galaxies around quasars
- Short Name:
- J/ApJ/740/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the association of galaxies with Ly{alpha} and OVI absorption, the most commonly detected transitions of the low-z intergalactic medium (IGM), in the fields of 14 quasars with z_em_=0.06-0.57. Confirming previous studies, we observe a high covering fraction for Ly{alpha} absorption to impact parameter {rho}=300h^-1^_72_kpc: 33/37 of our L>0.01L* galaxies show Ly{alpha} equivalent width W^Ly{alpha}^>=50 m{AA}. Galaxies of all luminosity L>0.01L* and spectral type are surrounded by a diffuse and ionized circumgalactic medium (CGM), whose baryonic mass is estimated at ~10^10.5^+/-0.3M_{sun}_ for a constant N_H_=10^19^cm^-2^. The virialized halos and extended CGM of present-day galaxies are responsible for most strong Ly{alpha} absorbers (W^Ly{alpha}^>300m{AA}) but cannot reproduce the majority of observed lines in the Ly{alpha} forest. We conclude that the majority of Ly{alpha} absorption with W^Ly{alpha}^=30-300m{AA} occurs in the cosmic web predicted by cosmological simulations and estimate a characteristic width for these filaments of ~400h^-1^_72_kpc. Regarding OVI, we observe a near unity covering fraction to {rho}=200h^-1^_72_kpc for L>0.1L* galaxies and to {rho}=300h^-1^_72_kpc for sub-L* (0.1 L*<L<L*) galaxies. Similar to our Ly{alpha} results, stronger OVI systems (W^1031^>70m{AA}) arise in the virialized halos of L>0.1L* galaxies. Unlike Ly{alpha}, the weaker OVI systems (W^1031^~30m{AA}) arise in the extended CGM of sub-L* galaxies. The majority of OVI gas observed in the low-z IGM is associated with a diffuse medium surrounding individual galaxies with L~0.3L* and rarely originates in the so-called warm-hot IGM (predicted by cosmological simulations.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A6
- Title:
- Ly{alpha}-[CII] velocity offsets in MS galaxies
- Short Name:
- J/A+A/643/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Lyman-{alpha} line in the ultraviolet (UV) and the [CII] line in the far-infrared (FIR) are widely used tools to identify galaxies in the early Universe and to obtain insights into interstellar medium (ISM) properties in high-redshift galaxies. By combining data obtained with ALMA in band 7 at ~320GHz as part of the ALMA Large Program to INvestigate [CII] at Early Times (ALPINE) with spectroscopic data from DEIMOS at the Keck Observatory, VIMOS and FORS2 at the Very Large Telescope, we assembled a unique sample of 53 main-sequence star-forming galaxies at 4.4<z<6 in which we detect both the Lyman-{alpha} line in the UV and the [CII] line in the FIR. The goal of this paper is to constrain the properties of the Ly{alpha} emission in these galaxies in relation to other properties of the ISM. We used [CII], observed with ALMA, as a tracer of the systemic velocity of the galaxies, and we exploited the available optical spectroscopy to obtain the Ly{alpha}-[CII] and ISM-[CII] velocity offsets. We find that 90% of the selected objects have Ly{alpha}-[CII] velocity offsets in the range 0<{Delta}v_Ly{alpha}-[CII]_<400km/s, in line with the few measurements available so far in the early Universe, and significantly smaller than those observed at lower redshifts. At the same time, we observe ISM-[CII] offsets in the range -500<{Delta}v_ISM-[CII]_<0km/s, in line with values at all redshifts, which we interpret as evidence for outflows in these galaxies. We find significant anticorrelations between {Delta}v_Ly{alpha}-[CII]_ and the Ly{alpha} rest-frame equivalent width EW_0_(Ly{alpha}) (or equivalently, the Ly{alpha} escape fraction f_esc_(Ly{alpha})): galaxies that show smaller {Delta}v_Ly{alpha}-[CII]_ have larger EW_0_(Ly{alpha}) and f_esc_(Ly{alpha}). We interpret these results in the framework of available models for the radiative transfer of Ly{alpha} photons. According to the models, the escape of Ly{alpha} photons would be favored in galaxies with high outflow velocities, producing large EW_0_(Ly{alpha}) and small {Delta}v_Ly{alpha}-[CII]_, in agreement with our observations. The uniform shell model would also predict that the Ly{alpha} escape in galaxies with slow outflows (0<v_out_<300km/s) is mainly determined by the neutral hydrogen column density (NHI) along the line of sight, while the alternative model by Steidel et al. (2010ApJ...717..289S) would more highly favor a combination of NHI at the systemic velocity and covering fraction as driver of the Ly{alpha} escape. We suggest that the increase in Ly{alpha} escape that is observed in the literature between z~2 and z~6 is not due to a higher incidence of fast outflows at high redshift, but rather to a decrease in average NHI along the line of sight, or alternatively, a decrease in HI covering fraction.
- ID:
- ivo://CDS.VizieR/J/ApJ/760/128
- Title:
- Ly{alpha} emission from 4<z<6 sources in COSMOS
- Short Name:
- J/ApJ/760/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate spectroscopically measured Ly{alpha} equivalent widths (EWs) and escape fractions of 244 sources of which 95 are Lyman break galaxies (LBGs) and 106 Lyman alpha emitters (LAEs) at z~4.2, z~4.8, and z~5.6 selected from intermediate and narrowband observations. The sources were selected from the Cosmic Evolution Survey and observed with the DEIMOS spectrograph. We find that the distribution of EWs shows no evolution with redshift for both the LBG selected sources and the intermediate/narrowband LAEs. We also find that the Ly{alpha} escape fraction of intermediate/narrowband LAEs is on average higher and has a larger variation than the escape fraction of LBG selected sources. The escape fraction does not show a dependence with redshift. Similar to what has been found for LAEs at low redshifts, the sources with the highest extinctions show the lowest escape fractions. The range of escape fractions increases with decreasing extinction. This is evidence that the dust extinction is the most important factor affecting the escape of Ly{alpha} photons, but at low extinctions other factors, such as the H I covering fraction and gas kinematics, can be just as effective at inhibiting the escape of Ly{alpha} photons.
- ID:
- ivo://CDS.VizieR/J/ApJ/667/79
- Title:
- Ly{alpha} emission-line galaxies at z=3.1
- Short Name:
- J/ApJ/667/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the results of an extremely deep, 0.28{deg}^2^ survey for z=3.1 Ly{alpha} emission-line galaxies in the Extended Chandra Deep Field-South. By using a narrowband 5000{AA} filter and complementary broadband photometry from the MUSYC survey, we identify a statistically complete sample of 162 galaxies with monochromatic fluxes brighter than 1.5x10^-17^ergs/cm^2^/s and observer's frame equivalent widths greater than 80{AA}
- ID:
- ivo://CDS.VizieR/J/A+A/431/793
- Title:
- Ly-alpha emitters around MRC 0316-257
- Short Name:
- J/A+A/431/793
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of the radio galaxy MRC 0316-257 at z=3.13 and the surrounding field resulted in the discovery of 77 candidate Ly{alpha} emitters with a rest-frame equivalent width of >15{AA}. 31 of 40 candidate emitters observed spectroscopically have redshifts similar to that of the radio galaxy. The properties of the Ly{alpha} emission line of the 31 confirmed emitters and the radio galaxy are presented in the file table2.dat (Table 2 in the paper). The magnitudes and continuum slopes of these z~3.1 galaxies are printed in the file table4.dat (Table 4 in the paper). The Ly{alpha} galaxies are faint, blue and small, consistent with the emitters being young starforming galaxies which are still nearly dust free.
- ID:
- ivo://CDS.VizieR/J/ApJ/903/4
- Title:
- 260 Ly{alpha} Emitters at Redshift z~5.7 with M2FS
- Short Name:
- J/ApJ/903/4
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- We present a spectroscopic survey of Ly{alpha} emitters (LAEs) at z~5.7 using the multiobject spectrograph M2FS on the Magellan Clay telescope. This is part of a high-redshift galaxy survey carried out in several well-studied deep fields. These fields have deep images in multiple UV/optical bands, including a narrow NB816 band that has allowed an efficient selection of LAE candidates at z~5.7. Our sample consists of 260 LAEs and covers a total effective area of more than 2deg^2^ on the sky. This is so far the largest (spectroscopically confirmed) sample of LAEs at this redshift. We use the secure redshifts and narrowband photometry to measure Ly{alpha} luminosities. We find that these LAEs span a Ly{alpha} luminosity range of ~2x10^42^-5x10^43^erg/s and include some of the most luminous galaxies known at z>=5.7 in terms of Ly{alpha} luminosity. Most of them have rest-frame equivalent widths between 20 and 300{AA}, and more luminous Ly{alpha} emission lines tend to have broader line widths. We detect a clear offset of ~20{AA} between the observed Ly{alpha} wavelength distribution and the NB816 filter transmission curve, which can be explained by the intergalactic medium absorption of continua blueward of Ly{alpha} in the high-redshift spectra. This sample is being used to study the Ly{alpha} luminosity function and galaxy properties at z~5.7.
- ID:
- ivo://CDS.VizieR/J/ApJ/696/546
- Title:
- Ly{alpha} emitters at z~4.86
- Short Name:
- J/ApJ/696/546
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a survey for Ly{alpha} emitters at z~4.86 based on optical narrowband ({lambda}c=7126{AA}, {Delta}{lambda}=73{AA}) and broadband (B, V, r', i', and z') observations of the Cosmic Evolution Survey field using Suprime-Cam on the Subaru Telescope. We find 79 Ly{alpha} emitter (LAE) candidates at z~4.86 over a contiguous survey area of 1.83deg^2^, down to the Ly{alpha} line flux of 1.47x10^-17^erg/s/cm^2^. We obtain the Ly{alpha} luminosity function with a best-fit Schechter parameters of log L*=42.9^+0.5^_-0.3_erg/s and {Phi}*=1.2^+8.0^_-1.1_x10^-4^Mpc^-3^ for {alpha}=-1.5 (fixed). The two-point correlation function for our LAE sample is {xi}(r)=(r/4.4^+5.7^_-2.9_Mpc)^-1.90+/-0.22^. In order to investigate the field-to-field variations of the properties of Ly{alpha} emitters, we divide the survey area into nine tiles of 0.5x0.5{deg} each. We find that the number density varies with a factor of ~2 from field to field with high statistical significance. However, we find no significant field-to-field variance when we divide the field into four tiles with 0.7x0.7{deg} each. We conclude that at least 0.5deg^2^ survey area is required to derive averaged properties of LAEs at z~5, and our survey field is wide enough to overcome the cosmic variance.
- 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).
