- ID:
- ivo://CDS.VizieR/J/ApJ/781/2
- Title:
- Redshifts of 1151 galaxies from SDSS
- Short Name:
- J/ApJ/781/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lines of sight with multiple projected cluster-scale gravitational lenses have high total masses and complex lens plane interactions that can boost the area of magnification, or etendue, making detection of faint background sources more likely than elsewhere. To identify these new "compound" cosmic telescopes, we have found directions in the sky with the highest integrated mass densities, as traced by the projected concentrations of luminous red galaxies (LRGs). We use new galaxy spectroscopy to derive preliminary magnification maps for two such lines of sight with total mass exceeding ~3x10^15^M_{sun}_. From 1151 MMT Hectospec spectra of galaxies down to i_AB_=21.2, we identify two to three group- and cluster-scale halos in each beam. These are well traced by LRGs. The majority of the mass in beam J085007.6+360428 (0850) is contributed by Zwicky 1953, a massive cluster at z=0.3774, whereas beam J130657.5+463219 (1306) is composed of three halos with virial masses of 6x10^14^-2x10^15^M_{sun}_, one of which is A1682. The magnification maps derived from our mass models based on spectroscopy and Sloan Digital Sky Survey photometry alone display substantial etendue: the 68% confidence bands on the lens plane area with magnification exceeding 10 for a source plane of z_s_=10 are [1.2,3.8]arcmin^2^ for 0850 and [2.3,6.7]arcmin^2^ for 1306. In deep Subaru Suprime-Cam imaging of beam 0850, we serendipitously discover a candidate multiply imaged V-dropout source at z_phot_=5.03. The location of the candidate multiply imaged arcs is consistent with the critical curves for a source plane of z=5.03 predicted by our mass model. Incorporating the position of the candidate multiply imaged galaxy as a constraint on the critical curve location in 0850 narrows the 68% confidence band on the lens plane area with {mu}>10 and z_s_=10 to [1.8,4.2]arcmin^2^, an etendue range comparable to that of MACS 0717+3745 and El Gordo, two of the most powerful single cluster lenses known. The significant lensing power of our beams makes them powerful probes of reionization and galaxy formation in the early universe.
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- ID:
- ivo://CDS.VizieR/J/A+A/618/A66
- Title:
- Redshifts of obscured AGN
- Short Name:
- J/A+A/618/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Redshifts are fundamental for our understanding of extragalactic X-ray sources. Ambiguous counterpart associations, expensive optical spectroscopy and/or multimission multiwavelength coverage to resolve degeneracies make estimation often difficult in practice. We attempt to constrain redshifts of obscured Active Galactic Nuclei (AGN) using only low-resolution X-ray spectra. Our XZ method fits AGN X-ray spectra with a moderately complex spectral model incorporating a corona, torus obscurer and warm mirror. Using the Bayesian X-ray Astronomy (BXA) package, we constrain redshift, column density, photon index and luminosity simultaneously. The redshift information primarily comes from absorption edges in Compton-thin AGN, and from the Fe K{alpha} fluorescent line in heavily obscured AGN. A new generic background fitting method allows us to extract more information from limited numbers of source counts. We derive redshift constraints for 74/321 hard-band detected sources in the Chandra deep field South. Comparing with spectroscopic redshifts, we find an outlier fraction of 8%, indicating that our model assumptions are valid. For three Chandra deep fields, we release our XZ redshift estimates. The independent XZ estimate is easy to apply and effective for a large fraction of obscured AGN in todays deep surveys without the need for any additional data. Comparing to different redshift estimation methods, XZ can resolve degeneracies in photometric redshifts, help to detect potential association problems and confirm uncertain single-line spectroscopic redshifts. With high spectral resolution and large collecting area, this technique will be highly effective for Athena/WFI observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/168
- Title:
- Redshift survey in the Subaru GTO2deg^2^ field
- Short Name:
- J/ApJ/750/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a dense redshift survey in the foreground of the Subaru GTO2deg^2^ weak-lensing field (centered at 16:04:44+43:11'24 (2000) to assess the completeness and comment on the purity of massive halo identification in the weak-lensing map. The redshift survey (published here) includes 4541 galaxies; 4405 are new redshifts measured with the Hectospec on the MMT. Among the weak-lensing peaks with a signal to noise greater than 4.25, 2/3 correspond to individual massive systems; this result is essentially identical to the Geller et al. (2010ApJ...709..832G) test of the Deep Lens Survey (DLS) field F2. The Subaru map, based on images in substantially better seeing than the DLS, enables detection of less massive halos at fixed redshift as expected. We demonstrate that the procedure adopted by Miyazaki et al. (2002ApJ...580L..97M) for removing some contaminated peaks from the weak-lensing map improves agreement between the lensing map and the redshift survey in the identification of candidate massive systems.
- ID:
- ivo://CDS.VizieR/J/AJ/162/193
- Title:
- Redshift survey nearby galaxy cluster A2626
- Short Name:
- J/AJ/162/193
- Date:
- 16 Mar 2022 00:18:57
- Publisher:
- CDS
- Description:
- New MMT/Hectospec spectroscopy centered on the galaxy cluster A2626 and covering a ~1.8deg^2^ area out to z~0.46 more than doubles the number of galaxy redshifts in this region. The spectra confirm four clusters previously identified photometrically. A2625, which was previously thought to be a close neighbor of A2626, is in fact much more distant. The new data show six substructures associated with A2626 and five more associated with A2637. There is also a highly collimated collection of galaxies and galaxy groups between A2626 and A2637 having at least three and probably four substructures. At larger scales, the A2626-A2637 complex is not connected to the Pegasus-Perseus filament.
- ID:
- ivo://CDS.VizieR/J/ApJ/840/78
- Title:
- Redshift survey of ALMA-identified SMGs in ECDFS
- Short Name:
- J/ApJ/840/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopic redshifts of S_870{mu}m_>~2mJy submillimeter galaxies (SMGs), which have been identified from the ALMA follow-up observations of 870{mu}m detected sources in the Extended Chandra Deep Field South (the ALMA-LESS survey). We derive spectroscopic redshifts for 52 SMGs, with a median of z=2.4+/-0.1. However, the distribution features a high-redshift tail, with ~23% of the SMGs at z>=3. Spectral diagnostics suggest that the SMGs are young starbursts, and the velocity offsets between the nebular emission and UV ISM absorption lines suggest that many are driving winds, with velocity offsets of up to 2000km/s. Using the spectroscopic redshifts and the extensive UV-to-radio photometry in this field, we produce optimized spectral energy distributions (SEDs) using Magphys, and use the SEDs to infer a median stellar mass of M_*_=(6+/-1)x10^10^M_{sun}_ for our SMGs with spectroscopic redshift. By combining these stellar masses with the star formation rates (measured from the far-infrared SEDs), we show that SMGs (on average) lie a factor of ~5 above the so-called "main sequence" at z~2. We provide this library of 52 template fits with robust and uniquely well-sampled SEDs as a resource for future studies of SMGs, and also release the spectroscopic catalog of ~2000 (mostly infrared-selected) galaxies targeted as part of the spectroscopic campaign.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/124
- Title:
- Redshift survey of the nearby galaxy cluster A2107
- Short Name:
- J/ApJ/869/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the rotational motion of the galaxy cluster A2107 at redshift z=0.04 and its connection to nearby large-scale structures using a large amount of spectroscopic redshift data. By combining 978 new redshifts from the MMT/Hectospec observations with data in the literature, we construct a large sample of 1968 galaxies with measured redshifts at clustercentric radius R<60'. Our sample has high (80%) and spatially uniform completeness at r-band apparent magnitude m_r,Petro,0_<19.1. We first apply the caustic method to the sample and identify 285 member galaxies of A2107 at R<60'. Then the rotation amplitude and the position angle of the rotation axis are measured. We find that the member galaxies show strong global rotation at R<20' (v_rot_/{sigma}_v_~0.6) with a significance of >3.8{sigma}, which is confirmed by two independent methods. The rotation becomes weaker in outer regions. There are at least five filamentary structures that are connected to the cluster and that consist of known galaxy groups. These structures are smoothly connected to the cluster, which seem to be inducing the global rotation of the cluster through inflow of galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/577/A18
- Title:
- Reduced CRIRES spectra around S multiplet 3
- Short Name:
- J/A+A/577/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sulphur is an important, volatile alpha element but its role in the Galactic chemical evolution is still uncertain. We derive the S abundances in RGB stars in three Galactic globular clusters (GC) that cover a wide metallicity range (-2.3<[Fe/H]<-1.2): M4, M22, and M30. The halo field stars show a large scatter in the [S/Fe] ratio in this metallicity span, which is inconsistent with canonical chemical evolution models. To date, very few measurements of [S/Fe] exist for stars in GCs, which are good tracers of the chemical enrichment of their environment. However, some light and alpha elements show star-to-star variations within individual GCs and it is yet unclear whether sulphur also varies between GC stars. We used the the infrared spectrograph CRIRES to obtain high-resolution (R~50000), high signal-to-noise (SNR~200 per px) spectra in the region of the SI multiplet 3 at 1045nm for 15 GC stars selected from the literature (6 stars in M4, 6 stars in M22 and 3 stars in M30). Multiplet 3 is better suited for S abundance derivation than the more commonly used lines of multiplet 1 at 920nm, since its lines are not blended by telluric absorption or other stellar features at low metallicity. We used spectral synthesis to derive the [S/Fe] ratio of the stars assuming local thermodynamic equilibrium (LTE). We find mean [S/Fe]=0.58+/-0.01+/-0.20dex (statistical and systematic error) for M4, [S/Fe]=0.57+/-0.01+/-0.19dex for M22, and [S/Fe]=0.55+/-0.02+/-0.16dex for M30. The negative NLTE corrections are estimated to be in the order of the systematic uncertainties. With the tentative exception of two stars with measured high S abundances, we conclude that sulphur behaves like a typical alpha element in the studied Galactic GCs, showing enhanced abundances with respect to the solar value at metallicities below [Fe/H]=-1.0dex without a considerable spread.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A142
- Title:
- Reduced high-resolution HI and CO data cubes
- Short Name:
- J/A+A/592/A142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intermediate-velocity clouds (IVCs) are HI halo clouds that are likely related to a Galactic fountain process. In-falling IVCs are candidates for the re-accretion of matter onto the Milky Way. Aims. We study the evolution of IVCs at the disk-halo interface, focussing on the transition from atomic to molecular IVCs. We compare an atomic IVC to a molecular IVC and characterise their structural differences in order to investigate how molecular IVCs form high above the Galactic plane. With high-resolution HI observations of the Westerbork Synthesis Radio Telescope and ^12^CO(1-0) and ^13^CO(1-0) observations with the IRAM 30m telescope, we analyse the small-scale structures within the two clouds. By correlating HI and far-infrared (FIR) dust continuum emission from the Planck satellite, the distribution of molecular hydrogen (H_2_) is estimated. We conduct a detailed comparison of the HI, FIR, and CO data and study variations of the XCO conversion factor. The atomic IVC does not disclose detectable CO emission. The atomic small-scale structure, as revealed by the high-resolution HI data, shows low peak HI column densities and low HI fluxes as compared to the molecular IVC. The molecular IVC exhibits a rich molecular structure and most of the CO emission is observed at the eastern edge of the cloud. There is observational evidence that the molecular IVC is in a transient and, thus, non- equilibrium phase. The average XCO factor is close to the canonical value of the Milky Way disk. We propose that the two IVCs represent different states in a gradual transition from atomic to molecular clouds. The molecular IVC appears to be more condensed allowing the formation of H_2_ and CO in shielded regions all over the cloud. Ram pressure may accumulate gas and thus facilitate the formation of H_2_. We show evidence that the atomic IVC will evolve also into a molecular IVC in a few Myr.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A31
- Title:
- Reduced spectra of NGC 6528 stars
- Short Name:
- J/A+A/601/A31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Here we explore robust ways of determining the iron content of metal-rich giant stars. We aim to understand what biases and shortcomings the widely applied methods suffer from. In this study we were mainly concerned with standard methods of analysing stellar spectra. These include the analysis of individual lines to determine stellar parameters, and analysis of the broad wings of certain lines (e.g. Halpha and calcium lines) to determine effective temperature and surface gravity for the stars. For NGC 6528 we find that [Fe/H]=+0.04dex with a scatter of 0.07dex, which gives an error in the derived mean abundance of 0.02dex. Our work has two important conclusions for analysis of metal-rich red giant branch stars. Firstly, for spectra with S/N of below about 35 per reduced pixel, [Fe/H] becomes too high. Secondly, determination of Teff using the wings of the H{alpha} line results in [Fe/H] values about 0.1dex higher than if excitational equilibrium is used. The last conclusion is perhaps unsurprising, as we expect the NLTE effect to become more prominent in cooler stars and we can not use the the wings of the H{alpha} line to determine Teff for the cool stars in our sample. We therefore recommend that in studies of metal-rich red giant stars care should be taken to obtain sufficient calibration data to enable use of the cooler stars.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A131
- Title:
- Reduced X-shooter spectra of GRB 190114A
- Short Name:
- J/A+A/629/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detections of molecular hydrogen (H_2_), vibrationally-excited H_2_ (H_2_*), and neutral atomic carbon (CI), an efficient tracer of molecular gas, in two new afterglow spectra of GRBs 181020A (z=2.938) and 190114A (z=3.376), observed with X-shooter at the Very Large Telescope (VLT). Both host-galaxy absorption systems are characterized by strong damped Lyman-alpha absorbers (DLAs) and substantial amounts of molecular hydrogen with logN(HI,H_2_)=22.20+/-0.05, 20.40+/-0.04 (GRB 181020A) and logN(HI, H_2_)=22.15+/-0.05, 19.44+/-0.04 (GRB 190114A). The DLA metallicites, depletion levels, and dust extinctions are within the typical regimes probed by GRBs with [Zn/H]=-1.57+/-0.06, [Zn/Fe]=0.67+/-0.03, and AV=0.27+/-0.02mag (GRB 181020A) and [Zn/H]=-1.23+/-0.07, [Zn/Fe]=1.06+/-0.08, and AV=0.36+/-0.02mag (GRB 190114A). In addition, we examine the molecular gas content of all known H2-bearing GRB-DLAs and explore the physical conditions and characteristics required to simultaneously probe CI and H_2_*. We confirm that H2 is detected in all CI- and H2*-bearing GRB absorption systems, but that these rarer features are not necessarily detected in all GRB H2 absorbers. We find that a large molecular fraction of f_H2_>~10^-3^ is required for CI to be detected. The defining characteristic for H_2_* to be present is less clear, though a large H_2_ column density is an essential factor. We also find that the observed line profiles of the molecular-gas tracers are kinematically "cold", with small velocity offsets of {delta}v<20km/s from the bulk of the neutral absorbing gas. We then derive the H_2_ excitation temperatures of the molecular gas and find that they are relatively low with Tex~=100-300K, however, there could be evidence of warmer components populating the high-J H_2_ levels in GRBs 181020A and 190114A. Finally, we demonstrate that even though the X-shooter GRB afterglow campaign has been successful in recovering several H2-bearing GRB-host absorbers, this sample is still hampered by a significant dust bias excluding the most dust-obscured H_2_ absorbers from identification. CI and H_2_* could open a potential route to identify molecular gas even in low-metallicity or highly dust-obscured bursts, though they are only efficient tracers for the most H2-rich GRB-host absorption systems.
