- 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.
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- 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/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/852/22
- Title:
- Ly{alpha} forest power spectrum at 1.8<=z<=3.4
- Short Name:
- J/ApJ/852/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new measurement of the Ly{alpha} forest power spectrum at 1.8<z<3.4 using 74 Keck/HIRES and VLT/UVES high-resolution, high-signal-to-noise-ratio quasar spectra. We developed a custom pipeline to measure the power spectrum and its uncertainty, which fully accounts for finite resolution and noise and corrects for the bias induced by masking missing data, damped Ly{alpha} absorption systems, and metal absorption lines. Our measurement results in unprecedented precision on the small-scale modes k>0.02s/km, inaccessible to previous SDSS/BOSS analyses. It is well known that these high-k modes are highly sensitive to the thermal state of the intergalactic medium, but contamination by narrow metal lines is a significant concern. We quantify the effect of metals on the small- scale power and find a modest effect on modes with k<0.1s/km. As a result, by masking metals and restricting to k<0.1s/km, their impact is completely mitigated. We present an end-to-end Bayesian forward-modeling framework whereby mock spectra with the same noise, resolution, and masking as our data are generated from Ly{alpha} forest simulations. These mock spectra are used to build a custom emulator, enabling us to interpolate between a sparse grid of models and perform Markov chain Monte Carlo fits. Our results agree well with BOSS on scales k<0.02s/km, where the measurements overlap. The combination of the percent-level low-k precision of BOSS with our 5%-15% high-k measurements results in a powerful new data set for precisely constraining the thermal history of the intergalactic medium, cosmological parameters, and the nature of dark matter.
- ID:
- ivo://CDS.VizieR/J/ApJ/457/102
- Title:
- Ly-Alpha Forest spectra simulation analysis. I.
- Short Name:
- J/ApJ/457/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present moderate-resolution (~50km/s FWHM) spectra of the Ly-alpha forest for seven quasars with redshifts ranging from 2.53 to 3.13, obtained with the Blue Spectrograph and photon-counting Reticon at the Multiple Mirror Telescope. Combined with spectra of 10 other quasars presented elsewhere, we have characterized the distribution of cloud properties in a way which was designed to minimize any subjective part of the analysis. We used artificial absorption spectra, with the same resolution, sampling and signal-to-noise ratio as a function of wavelength as the actual data. Distributions of the physical parameters of the Ly-alpha clouds, namely, the neutral hydrogen column density (N) and Doppler parameter (b), were approximated with d"N"/dN proportional to N^(-beta) and d"N"/db proportional to exp[-(b-<b>)^2/(2 sigma_b^2)], respectively. We constructed a grid of simulated spectra with different input parameters. Comparison of properties of the simulated spectra with the observed spectra yielded acceptable ranges of parameters. Our technique differs from previous similar work in that we use the information contained in the distribution of the strength of the absorption in each resolution element and the distribution of separations between absorption complexes. We derive beta =1.4+/-0.1 for N ranging from 10^13 to 10^16cm^-2 and <b>=30+/-15km/s. Most previous studies based on line lists indicated beta=1.7-1.9. We attribute this difference to flattening of the column density distribution for low N, recently confirmed by higher resolution observations. Our result for <b>, though consistent with values quoted in the literature, is of lower significance, since it is less than the resolution of our spectra. We conclude by commenting on the importance of line blending in data sets of this kind.
- 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/886/19
- Title:
- Ly{alpha} obs. of low-mass stars Ross 825 & 1044
- Short Name:
- J/ApJ/886/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of habitable zone (HZ) planets around low-mass stars has highlighted the need for a comprehensive understanding of the radiation environments in which such planets reside. Of particular importance is knowledge of the far-ultraviolet (FUV) radiation, as low-mass stars are typically much more active than solar-type stars and the proximity of their HZs can be one-tenth the distance. The vast majority of the flux emitted by low-mass stars at FUV wavelengths occurs in the Ly{alpha} line at 1216 {AA}. However, measuring a low-mass star's Ly{alpha} emission directly is almost always impossible because of the contaminating effects of interstellar hydrogen and geocoronal airglow. We observed Ross825 (K3) and Ross1044 (M0), two stars with exceptional radial velocities, with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Their radial velocities resulted in significant line shifts, allowing for a more complete view of their Ly{alpha} line profiles. We provide an updated relation between effective temperature and Ly{alpha} flux using Gaia DR2 astrometry as well as updated, model-independent relationships between Ly{alpha} flux and UV flux measurements from the Galaxy Evolution Explorer (GALEX) for low-mass stars. These new relations, in combination with GALEX's considerable spatial coverage, provide substantial predictive power for the Ly{alpha} environments for thousands of nearby, low-mass stars.
- 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/ApJ/751/29
- Title:
- Ly{alpha} profiles of LAEs at z=3.1
- Short Name:
- J/ApJ/751/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the observations of the Ly{alpha} line profiles of 91 emission-line galaxies at z=3.1 with a spectral resolution of {lambda}/{delta}{lambda}(FWHM){approx}1700 or 180km/s. A significant fraction of ~50% of the observed objects show the characteristic double peaks in their Ly{alpha} profile. The red peak is much stronger than the blue one for most of the cases. The red peaks themselves also show weak but significant asymmetry and their widths are correlated with the velocity separation of the red and the blue peaks. This implies that the peaks are not isolated multiple components with different velocities but parts of a single line that are modified by the absorption and/or scattering by the associated neutral hydrogen gas. The characteristic profile can be naturally explained by scattering in the expanding shell of the neutral hydrogen surrounding the Ly{alpha} emitting region while the attenuation by the intergalactic medium should also be considered. Our results suggest that the star formation in these Ly{alpha} emitters are dominated by young burst-like events that produce the intrinsic Ly{alpha} emission as well as the gas outflow.
- ID:
- ivo://CDS.VizieR/J/A+A/458/427
- Title:
- Lyman alpha absorbers in 0.5<z<1.9 QSOs
- Short Name:
- J/A+A/458/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the evolution and the statistical properties of the Ly{alpha} absorbers of the intergalactic medium (IGM) in the largely unexplored redshift range z=0.5-1.9. We use high-resolution (R>=30000) UV (STIS) and optical (VLT/UVES and Keck/HIRES) spectra of nine bright quasars with z_em_<1.94. The Ly{alpha} lines detected in the lines of sight (LOS) towards these quasars are evaluated with a software package which determines simultaneously the quasar continuum and the line profiles.
