- ID:
- ivo://CDS.VizieR/J/ApJ/859/53
- Title:
- Ly{alpha} candidates from a MUSE survey of 6 AGNs
- Short Name:
- J/ApJ/859/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent theoretical models suggest that the early phase of galaxy formation could involve an epoch when galaxies are gas rich but inefficient at forming stars: a "dark galaxy" phase. Here, we report the results of our Multi-Unit Spectroscopic Explorer (MUSE) survey for dark galaxies fluorescently illuminated by quasars at z>3. Compared to previous studies which are based on deep narrowband (NB) imaging, our integral field survey provides a nearly uniform sensitivity coverage over a large volume in redshift space around the quasars as well as full spectral information at each location. Thanks to these unique features, we are able to build control samples at large redshift distances from the quasars using the same data taken under the same conditions. By comparing the rest-frame equivalent width (EW0) distributions of the Ly{alpha} sources detected in proximity to the quasars and in control samples, we detect a clear correlation between the locations of high-EW0 objects and the quasars. This correlation is not seen in other properties, such as Ly{alpha} luminosities or volume overdensities, suggesting the possible fluorescent nature of at least some of these objects. Among these, we find six sources without continuum counterparts and EW0 limits larger than 240{AA} that are the best candidates for dark galaxies in our survey at z>3.5. The volume densities and properties, including inferred gas masses and star formation efficiencies, of these dark galaxy candidates are similar to those of previously detected candidates at z~2.4 in NB surveys. Moreover, if the most distant of these are fluorescently illuminated by the quasar, our results also provide a lower limit of t=60Myr on the quasar lifetime.
Number of results to display per page
Search Results
- 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/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/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/other/NewA/51.59
- Title:
- LY And photometric followup
- Short Name:
- J/other/NewA/51.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a low-dispersion spectrum and two sets of CCD photometric light curves of the eclipsing binary LY And for the first time. The spectrum of LY And was classified as G2. We derived an updated ephemeris based on all previously available and our newly acquired minimum light times. Our analyses of LY And light curve minimum times reveals that the differences between calculated and observed minimum times for LY And can be represented by an upward parabolic curve, which means its orbital period is increasing with a rate of 1.88 (+/-0.13)x10^-7^days/year. This increase in orbital period may be interpreted as mass transfer from the primary component to the secondary component, with a rate of dM1/dt=-4.54x10^-8^M_{sun}_/year. By analyzing our CCD photometric light curves obtained in 2015, we obtained its photometric solution with the Wilson-Devinney program. This photometric solution also fits very well our light curves obtained in 2014. Our photometric solution shows that LY And is a contact eclipsing binary and its contact factor is f=(17.8+/-1.9)%. Furthermore, both our spectroscopic and photometric data show no obvious chromospheric activity of LY And.
- 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/642/A55
- Title:
- Lyman {alpha} blob LAB 1 MUSE data
- Short Name:
- J/A+A/642/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lyman {alpha} blobs (LABs) are large-scale radio-quiet Lyman {alpha} (Ly{alpha}) nebula at high-z that occur predominantly in overdense proto-cluster regions. In particular, there is the prototypical SSA22a-LAB1 at z=3.1 which has become an observational reference. We want to understand the powering mechanisms that drive the LAB so that we may gain empirical insights into the galaxy-formation processes within a rare dense environment at high-z. Thus, we need to infer the distribution, the dynamics, and the ionisation state of LAB 1's Ly{alpha} emitting gas. LAB 1 was observed for 17.2h with the VLT/MUSE integral-field spectrograph. We produced optimally extracted narrow band images, in Ly{alpha} {lambda}1216, HeII {lambda}1640, and we tried to detect CIV {lambda}1549 emission. By utilising a moment-based analysis, we mapped the kinematics and the line profile characteristics of the blob. We also linked the inferences from the line profile analysis to previous results from imaging polarimetry. We map Ly{alpha} emission from the blob down to surface-brightness limits of ~6x10^-19^erg/s/cm^2^/arcsec^2^. At this depth, we reveal a bridge between LAB 1 and its northern neighbour LAB 8, as well as a shell-like filament towards the south of LAB 1. The complexity and morphology of the Ly{alpha} profile vary strongly throughout the blob. Despite the complexity, we find a coherent large-scale east-west velocity gradient of ~1000km/s that is aligned perpendicular to the major axis of the blob. Moreover, we observe a negative correlation of Ly{alpha} polarisation fraction with Ly{alpha} line width and a positive correlation with absolute line-of-sight velocity. Finally, we reveal HeII emission in three distinct regions within the blob, however, we can only provide upper limits for CIV. Various gas excitation mechanisms are at play in LAB 1: ionising radiation and feedback effects dominate near the embedded galaxies, while Ly{alpha} scattering contributes at larger distances. However, HeII/Ly{alpha} ratios combined with upper limits on CIV/Ly{alpha} are not able to discriminate between active galactic nucleus (AGN) ionisation and feedback-driven shocks. The alignment of the angular momentum vector parallel to the morphological principal axis appears to be at odds with the predicted norm for high-mass halos, but this most likely reflects that LAB 1 resides at a node of multiple intersecting filaments of the cosmic web. LAB 1 can thus be thought of as a progenitor of a present-day massive elliptical within a galaxy cluster.
- ID:
- ivo://CDS.VizieR/J/ApJ/736/48
- Title:
- 48 Lyman break galaxies at z~3 in HUDF
- Short Name:
- J/ApJ/736/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present evidence for spatially extended low surface brightness emission around Lyman break galaxies (LBGs) in the V-band image of the Hubble Ultra Deep Field, corresponding to the z~3 rest-frame far-UV (FUV) light, which is a sensitive measure of star formation rates (SFRs). We find that the covering fraction of molecular gas at z~3 is not adequate to explain the emission in the outskirts of LBGs, while the covering fraction of neutral atomic-dominated hydrogen gas at high redshift is sufficient. We develop a theoretical framework to connect this emission around LBGs to the expected emission from neutral HI gas, i.e., damped Ly{alpha} systems (DLAs), using the Kennicutt-Schmidt (KS) relation. Working under the hypothesis that the observed FUV emission in the outskirts of LBGs is from in situ star formation in atomic-dominated hydrogen gas, the results suggest that the SFR efficiency in such gas at z~3 is between factors of 10 and 50 lower than predictions based on the local KS relation. The total SFR density in atomic-dominated gas at z~3 is constrained to be ~10% of that observed from the inner regions of LBGs. In addition, the metals produced by in situ star formation in the outskirts of LBGs yield metallicities comparable to those of DLAs, which is a possible solution to the "Missing Metals" problem for DLAs. Finally, the atomic-dominated gas in the outskirts of galaxies at both high and low redshifts has similar reduced SFR efficiencies and is consistent with the same power law.
- ID:
- ivo://CDS.VizieR/J/ApJ/736/18
- Title:
- Lyman-continuum emission at z~3 in SSA22 field
- Short Name:
- J/ApJ/736/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an ultradeep, narrowband imaging survey for Lyman-continuum (LyC) emission at z~3 in the SSA22a field. We employ a custom narrowband filter centered at {lambda}=3640{AA} (NB3640), which probes the LyC region for galaxies at z>=3.06. We also analyze new and archival NB4980 imaging tuned to the wavelength of the Ly{alpha} emission line at z=3.09, and archival broadband B, V, and R images of the non-ionizing UV continuum. Our NB3640 images contain 26 z>=3.06 Lyman break galaxies (LBGs) as well as a set of 130 Ly{alpha} emitters (LAEs), identified by their excess NB4980 flux relative to the BV continuum. Six LBGs and 28 LAEs are detected in the NB3640 image. LBGs appear to span a range of NB3640-R colors, while LAEs appear bimodal in their NB3640-R properties. We estimate average UV-to-LyC flux density ratios.
