- 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.
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Search Results
- 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/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/884/151
- Title:
- Lyman cont. luminosity of SDSS quasar pairs at z~3
- Short Name:
- J/ApJ/884/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used spectra of 181 projected quasar pairs at separations <=1.5' from the Sloan Digital Sky Survey Data Release 12 in the redshift range of 2.5-3.5 to probe the proximity regions of the foreground quasars. We study the proximity effect both in the longitudinal and in the transverse directions, by carrying out a comparison of the Ly{alpha} absorption lines originating from the vicinity of quasars to those originating from the general intergalactic medium at the same redshift. We found an enhancement in the transmitted flux within 4Mpc to the quasar in the longitudinal direction. However, the trend is found to be reversed in the transverse direction. In the longitudinal direction, we derived an excess overdensity profile showing an excess up to r<=5Mpc after correcting for the quasar's ionization, taking into account the effect of low spectral resolution. This excess overdensity profile matches with the average overdensity profile in the transverse direction without applying any correction for the effect of the quasar's ionization. Among various possible interpretations, we found that the anisotropic obscuration of the quasar's ionization seems to be the most probable explanation. This is also supported by the fact that all of our foreground quasars happen to be type 1 AGNs. Finally, we constrain the average quasar's illumination along the transverse direction as compared to that along the longitudinal direction to be <=27% (3{sigma} confidence level).
- ID:
- ivo://CDS.VizieR/J/ApJS/240/33
- Title:
- MaDCoWS. I. Catalog of z~1 galaxy clusters
- Short Name:
- J/ApJS/240/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Massive and Distant Clusters of WISE Survey (MaDCoWS), a search for galaxy clusters at 0.7<=z<=1.5 based upon data from the Wide-field Infrared Survey Explorer (WISE) mission. MaDCoWS is the first cluster survey capable of discovering massive clusters at these redshifts over the full extragalactic sky. The search is divided into two regions-the region of the extragalactic sky covered by Pan-STARRS ({delta}{>}-30{deg}) and the remainder of the southern extragalactic sky at {delta}{<}-30{deg} for which shallower optical data from the SuperCOSMOS Sky Survey is available. In this paper, we describe the search algorithm, characterize the sample, and present the first MaDCoWS data release-catalogs of the 2433 highest amplitude detections in the WISE-Pan-STARRS region and the 250 highest amplitude detections in the WISE-SuperCOSMOS region. A total of 1723 of the detections from the WISE-Pan-STARRS sample have also been observed with the Spitzer Space Telescope, providing photometric redshifts and richnesses, and an additional 64 detections within the WISE-SuperCOSMOS region also have photometric redshifts and richnesses. Spectroscopic redshifts for 38 MaDCoWS clusters with IRAC photometry demonstrate that the photometric redshifts have an uncertainty of {sigma}z/(1+z)~0.036. Combining the richness measurements with Sunyaev-Zel'dovich observations of MaDCoWS clusters, we also present a preliminary mass-richness relation that can be used to infer the approximate mass distribution of the full sample. The estimated median mass for the WISE-Pan-STARRS catalog is M_500_=1.6_-0.8_^+0.7^x10^14^M_{sun}_, with the Sunyaev-Zel'dovich data confirming that we detect clusters with masses up to M_500_~5x10^14^M_{sun}_ (_M200_~10^15^M_{sun}_).
- ID:
- ivo://CDS.VizieR/J/AJ/162/229
- Title:
- 13 Magellanic Clouds metal-poor stars
- Short Name:
- J/AJ/162/229
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- The chemical abundances of a galaxy's metal-poor stellar population can be used to investigate the earliest stages of its formation and chemical evolution. The Magellanic Clouds are the most massive of the Milky Way's satellite galaxies and are thought to have evolved in isolation until their recent accretion by the Milky Way. Unlike the Milky Way's less massive satellites, little is known about the Magellanic Clouds' metal-poor stars. We have used the mid-infrared metal-poor star selection of Schlaufman & Casey and archival data to target nine LMC and four SMC giants for high-resolution Magellan/MIKE spectroscopy. These nine LMC giants with -2.4<~[Fe/H]<~-1.5 and four SMC giants with -2.6<~[Fe/H]<~-2.0 are the most metal-poor stars in the Magellanic Clouds yet subject to a comprehensive abundance analysis. While we find that at constant metallicity these stars are similar to Milky Way stars in their {alpha}, light, and iron-peak elemental abundances, both the LMC and SMC are enhanced relative to the Milky Way in the r-process element europium. These abundance offsets are highly significant, equivalent to 3.9{sigma} for the LMC, 2.7{sigma} for the SMC, and 5.0{sigma} for the complete Magellanic Cloud sample. We propose that the r-process enhancement of the Magellanic Clouds' metal-poor stellar population is a result of the Magellanic Clouds' isolated chemical evolution and long history of accretion from the cosmic web combined with r-process nucleosynthesis on a timescale longer than the core-collapse supernova timescale but shorter than or comparable to the thermonuclear (i.e., Type Ia) supernova timescale.
- 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/819/53
- Title:
- Magellan/M2FS spectroscopy of Tucana 2 and Grus 1
- Short Name:
- J/ApJ/819/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from spectroscopic observations with the Michigan/Magellan Fiber System (M2FS) of 147 stellar targets along the line of sight to the newly discovered "ultrafaint" stellar systems Tucana 2 (Tuc 2) and Grus 1 (Gru 1). Based on simultaneous estimates of line of sight velocity and stellar-atmospheric parameters, we identify 8 and 7 stars as probable members of Tuc 2 and and Gru 1, respectively. Our sample for Tuc 2 is sufficient to resolve an internal velocity dispersion of 8.6^+4.4^_-2.7_km/s about a mean of -129.1+/-3.5km/s (solar rest frame), and to estimate a mean metallicity of [Fe/H]=-2.23^+0.18^_-0.12_. These results place Tuc 2 on chemodynamical scaling relations followed by dwarf galaxies, suggesting a dominant dark matter component with dynamical mass 2.7^+3.1^_-1.3_x10^6^M_{sun}_ enclosed within the central ~160pc, and dynamical mass-to-light ratio 1913^+2234^_-950_M_{sun}_/L_{nu},{sun}_. For Gru 1 we estimate a mean velocity of -140.5^+2.4^_-1.6_km/s and a mean metallicity of [Fe/H]=-1.42^+0.55^_-0.42_ but our sample does not resolve Gru 1's velocity dispersion. The radial coordinates of Tuc 2 and Gru 1 in Galactic phase space suggest that their orbits are among the most energetic within a distance of <~300pc. Moreover, their proximity to each other in this space arises naturally if both objects are trailing the Large Magellanic Cloud.
- ID:
- ivo://CDS.VizieR/J/ApJ/857/145
- Title:
- MagLiteS Carina II and Carina III spectroscopy
- Short Name:
- J/ApJ/857/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Magellan/IMACS, Anglo-Australian Telescope/AAOmega+2dF, and Very Large Telescope/GIRAFFE+FLAMES spectroscopy of the Carina II (CarII) and Carina III (CarIII) dwarf galaxy candidates, recently discovered in the Magellanic Satellites Survey (MagLiteS). We identify 18 member stars in Car II, including two binaries with variable radial velocities and two RR Lyrae stars. The other 14 members have a mean heliocentric velocity v_hel_=477.2+/-1.2km/s and a velocity dispersion of {sigma}_v_=3.4_-0.8_^+1.2^km/s. Assuming Car II is in dynamical equilibrium, we derive a total mass within the half-light radius of 1.0_-0.4_^+0.8^x10^6^M_{sun}_, indicating a mass-to-light ratio of 369_-161_^+309^M_{sun}_/L_{sun}_. From equivalent width measurements of the calcium triplet lines of nine red giant branch (RGB) stars, we derive a mean metallicity of [Fe/H]=-2.44+/-0.09 with dispersion {sigma}_[Fe/H]_=0.22_-0.07_^+0.10^. Considering both the kinematic and chemical properties, we conclude that CarII is a dark-matter-dominated dwarf galaxy. For CarIII, we identify four member stars, from which we calculate a systemic velocity of v_hel_=284.6_-3.1_^+3.4^km/s. The brightest RGB member of CarIII has a metallicity of [Fe/H]=-1.97+/-0.12. Due to the small size of the Car III spectroscopic sample, we cannot conclusively determine its nature. Although these two systems have the smallest known physical separation ({Delta}d~10kpc) among Local Group satellites, the large difference in their systemic velocities, ~200km/s, indicates that they are unlikely to be a bound pair. One or both systems are likely associated with the Large Magellanic Cloud (LMC), and may remain LMC satellites today. No statistically significant excess of {gamma}-ray emission is found at the locations of Car II and Car III in eight years of Fermi-LAT data.
- ID:
- ivo://CDS.VizieR/J/AJ/159/114
- Title:
- Magnetic CVs spectra & other variable objects II.
- Short Name:
- J/AJ/159/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper of a series presenting our search for magnetic cataclysmic variables (mCVs) among candidates selected mostly from the Catalina Real-Time Transient Survey. We present the identification spectra, obtained at the SOAR Telescope, as well as magnitudes and Gaia distances for 45 objects. Of these, 39 objects are identified as CVs, from which 8 targets show observational characteristics of mCVs, being 7 polars and 1 intermediate polar. The remaining 31 CVs in our sample are probably non-magnetic systems, in low (22 systems) or high (9 systems) accretion states. Six targets of the sample are not CVs (5 active galactic nuclei and 1 T-Tauri star). Among the 8 objects with mCV spectra, 6 are new classifications. Three polars were observed in low-accretion state, either revealing photospheric features of the secondary star and allowing the estimation of their spectral type, or presenting H{beta} Zeeman components associated to the white dwarf (WD) magnetic field. In addition to the results obtained in the first paper of the series, and depending on the confirmation of these classifications by observational follow-up, our results would increase the sample of known polars by about 9%.