- 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.
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Search Results
- 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).
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/267
- Title:
- Ly{alpha} fluxes of HDFS 2.91<z<6.64 sources
- Short Name:
- J/MNRAS/471/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first estimate of the Ly{alpha} luminosity function using blind spectroscopy from the Multi Unit Spectroscopic Explorer, MUSE, in the Hubble Deep Field-South. Using automatic source-detection software, we assemble a homogeneously detected sample of 59 Ly{alpha} emitters covering a flux range of -18.0<log_10_(F)<-16.3(erg/s/cm2), corresponding to luminosities of 41.4<log_10_(L)<42.8(erg/s). As recent studies have shown, Ly{alpha} fluxes can be underestimated by a factor of 2 or more via traditional methods, and so we undertake a careful assessment of each object's Ly{alpha} flux using a curve-of-growth analysis to account for extended emission. We describe our self-consistent method for determining the completeness of the sample, and present an estimate of the global Ly {alpha} luminosity function between redshifts 2.91<z<6.64 using the 1/V_max_ estimator. We find that the luminosity function is higher than many number densities reported in the literature by a factor of 2-3, although our result is consistent at the 1{sigma} level with most of these studies. Our observed luminosity function is also in good agreement with predictions from semi-analytic models, and shows no evidence for strong evolution between the high- and low-redshift halves of the data. We demonstrate that one's approach to Ly{alpha} flux estimation does alter the observed luminosity function, and caution that accurate flux assessments will be crucial in measurements of the faint-end slope. This is a pilot study for the Ly{alpha} luminosity function in the MUSE deep-fields, to be built on with data from the Hubble Ultra Deep Field that will increase the size of our sample by almost a factor of 10.
- 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.
