- ID:
- ivo://CDS.VizieR/J/ApJ/883/157
- Title:
- Spectrophotometric redshifts of GOODS galaxies
- Short Name:
- J/ApJ/883/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the accuracy of 4000{AA}/Balmer-break based redshifts by combining Hubble Space Telescope (HST) grism data with photometry. The grism spectra are from the Probing Evolution And Reionization Spectroscopically survey with HST using the G800L grism on the Advanced Camera for Surveys. The photometric data come from a compilation by the 3D-HST collaboration of imaging from multiple surveys (notably, the Cosmic Assembly Near-infrared Deep Extragalactic Survey (CANDELS) and 3D-HST). We show evidence that spectrophotometric redshifts (SPZs) typically improve the accuracy of photometric redshifts by ~17%-60%. Our SPZ method is a template-fitting-based routine that accounts for correlated data between neighboring points within grism spectra via the covariance matrix formalism and also accounts for galaxy morphology along the dispersion direction. We show that the robustness of the SPZ is directly related to the fidelity of the D4000 measurement. We also estimate the accuracy of continuum-based redshifts, i.e., for galaxies that do not contain strong emission lines, based on the grism data alone ({sigma}_{Delta}z/(1+z)_^NMAD^<~0.06). Given that future space-based observatories like Wide Field InfraRed Survey Telescope and Euclid will spend a significant fraction of time on slitless spectroscopic observations, we estimate number densities for objects with |{Delta}z/(1+z_s_)|<=0.02. We predict ~700-4400 galaxies degree^-2^ for galaxies with D4000>1.1 and |{Delta}z/(1+z_s_)|<=0.02 to a limiting depth of i_AB_=24mag. This is especially important in the absence of an accompanying rich photometric data set like the existing one for the CANDELS fields, where redshift accuracy from future surveys will rely only on the presence of a feature like the 4000{AA}/Balmer breaks or the presence of emission lines within the grism spectra.
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- ID:
- ivo://CDS.VizieR/J/ApJ/695/1591
- Title:
- Spectrophotometry in PEARS fields
- Short Name:
- J/ApJ/695/1591
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep ACS slitless grism observations and identification of stellar sources are presented within the Great Observatories Origins Deep Survey North and South fields which were obtained in the Probing Evolution And Reionization Spectroscopically (PEARS) program. It is demonstrated that even low-resolution spectra can be a very powerful means of identifying stars in the field, especially low-mass stars with stellar types M0 and later. The PEARS fields lay within the larger GOODS fields, and we used new, deeper images to further refine the selection of stars in the PEARS field, down to a magnitude of z_850_=25 using a newly developed stellarity parameter. The total number of stars with reliable spectroscopic and morphological identification was 95 and 108 in the north and south fields, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJS/126/331
- Title:
- Spectrophotometry of nearby field galaxies
- Short Name:
- J/ApJS/126/331
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained integrated and nuclear spectra as well as U, B, R surface photometry for a representative sample of 196 nearby galaxies. These galaxies span the entire Hubble sequence in morphological type, as well as a wide range of luminosities (M_B_=-14 to -22). Here we present the spectrophotometry for these galaxies. The selection of the sample and the U, B, R surface photometry is described in a companion paper (J/ApJS/126/271).
- ID:
- ivo://CDS.VizieR/J/ApJ/815/49
- Title:
- Spectropolarimetric survey of radio sources
- Short Name:
- J/ApJ/815/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a broadband spectropolarimetric survey of 563 discrete, mostly unresolved radio sources between 1.3 and 2.0 GHz using data taken with the Australia Telescope Compact Array. We have used rotation-measure synthesis to identify Faraday-complex polarized sources, those objects whose frequency-dependent polarization behavior indicates the presence of material possessing complicated magnetoionic structure along the line of sight (LOS). For sources classified as Faraday-complex, we have analyzed a number of their radio and multiwavelength properties to determine whether they differ from Faraday-simple polarized sources (sources for which LOS magnetoionic structures are comparatively simple) in these properties. We use this information to constrain the physical nature of the magnetoionic structures responsible for generating the observed complexity. We detect Faraday complexity in 12% of polarized sources at ~1' resolution, but we demonstrate that underlying signal-to-noise limitations mean the true percentage is likely to be significantly higher in the polarized radio source population. We find that the properties of Faraday-complex objects are diverse, but that complexity is most often associated with depolarization of extended radio sources possessing a relatively steep total intensity spectrum. We find an association between Faraday complexity and LOS structure in the Galactic interstellar medium (ISM) and claim that a significant proportion of the Faraday complexity we observe may be generated at interfaces of the ISM associated with ionization fronts near neutral hydrogen structures. Galaxy cluster environments and internally generated Faraday complexity provide possible alternative explanations in some cases.
- ID:
- ivo://CDS.VizieR/J/A+A/442/211
- Title:
- Spectroscopic distances of 322 NLTT stars
- Short Name:
- J/A+A/442/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Distance estimates based on low-resolution spectroscopy and Two Micron All Sky Survey (2MASS, Cat. <II/246>) J magnitudes are presented for 322 nearby candidates from Luyten's NLTT catalogue (<I/98>). Mainly relatively bright (typically 7<Ks<11) and red high proper motion stars have been selected according to their 2MASS magnitudes and optical-to-infrared colours (+1<R-Ks<+7). Some LHS stars previously lacking spectroscopy have also been included. We have classified the majority of the objects as early-M dwarfs (M2-M5). More than 70% of our targets turned out to lie within the 25pc horizon of the catalogue of nearby stars, with 50 objects placed within 15pc and 8 objects being closer than 10pc. Three objects in the 10pc sample have no previously published spectral type: LP 876-10 (M4), LP 870-65 (M4.5), and LP 869-26 (M5). A large fraction of the objects in our sample (57%) ave independent distance estimates, mainly by the recent efforts of Reid and collaborators. Our distance determinations are generally in good agreement with theirs. 11 rather distant (d>100pc) objects have also been identified, including a probable halo, but relatively hot (Teff=13000K) white dwarf (LHS 1200) and 10 red dwarfs with extremely large tangential velocities (250<v_t_<1150km/s). Altogether, there are 11 red dwarfs (including one within 70pc) with tangential velocities larger than about 250km/s. All these objects are suspected to be in fact subdwarfs, if so, their distances would be only about half of our original estimates. The three most extreme objects in that respect are the K and early M dwarfs LP 323-168, LHS 5343 and LP 552-21 with corrected distances between 180pc and 400pc and resulting tangential velocities still larger than about 400km/s.
- ID:
- ivo://CDS.VizieR/J/ApJS/250/26
- Title:
- Spectroscopic follow-up of the QUBRICS quasars
- Short Name:
- J/ApJS/250/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the spectroscopic follow-up of the QUasars as BRIght beacons for Cosmology in the Southern Hemisphere (QUBRICS; Calderone+ 2019, J/ApJ/887/268) survey. The selection method is based on a machine-learning approach applied to photometric catalogs, covering an area of ~12400deg^2^ in the Southern Hemisphere. The spectroscopic observations started in 2018 and identified 55 new, high-redshift (z>=2.5), bright (i<=18) quasi-stellar objects (QSOs), with the catalog published in late 2019. Here we report the current status of the survey, bringing the total number of bright QSOs at z>=2.5 identified by QUBRICS to 224. The success rate of the QUBRICS selection method, in its most recent training, is estimated to be 68%. The predominant contaminant turns out to be lower-z QSOs at z<2.5. This survey provides a unique sample of bright QSOs at high z available for a number of cosmological investigations. In particular, carrying out the redshift drift measurements (Sandage Test) in the Southern Hemisphere, using the High Resolution Spectrograph at the 39m Extremely Large Telescope appears to be possible with less than 2500hr of observations spread over 30 targets in 25yr.
- ID:
- ivo://CDS.VizieR/J/ApJS/219/29
- Title:
- Spectroscopic redshifts in strong lens fields
- Short Name:
- J/ApJS/219/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the spectroscopic redshift catalog from a wide-field survey of the fields of 28 galaxy-mass strong gravitational lenses. We discuss the acquisition and reduction of the survey data, collected over 40 nights of 6.5m MMT and Magellan time, employing four different multiobject spectrographs. We determine that no biases are introduced by combining data sets obtained with different telescope and spectrograph combinations. Special care is taken to determine redshift uncertainties using repeat observations. The redshift catalog consists of 9768 new and unique galaxy redshifts. 82.4% of the catalog redshifts are between z=0.1 and z=0.7, and the catalog median redshift is z_med_=0.36. The data from this survey will be used to study the lens environments and line-of-sight structures to gain a better understanding of the effects of large-scale structure on lens statistics and lens-derived parameters.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/139
- Title:
- Spectroscopic redshifts of galaxies in groups
- Short Name:
- J/ApJ/756/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the global group properties of two samples of galaxy groups containing 39 high-quality X-ray-selected systems and 38 optically (spectroscopically) selected systems in coincident spatial regions at 0.12<z<0.79. The total mass range of the combined sample is ~(10^12^-5)x10^14^M_{sun}_. Only nine optical systems are associable with X-ray systems. We discuss the confusion inherent in the matching of both galaxies to extended X-ray emission and of X-ray emission to already identified optical systems. Extensive spectroscopy has been obtained and the resultant redshift catalog and group membership are provided here. X-ray, dynamical, and total stellar masses of the groups are also derived and presented. We explore the effects of utilizing different centers and applying three different kinds of radial cut to our systems: a constant cut of 1Mpc and two r_200_ cuts, one based on the velocity dispersion of the system and the other on the X-ray emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/138
- Title:
- Spectroscopic survey of bright white dwarfs
- Short Name:
- J/ApJ/743/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a spectroscopic survey of over 1300 bright (V<=17.5), hydrogen-rich white dwarfs based largely on the last published version of the McCook & Sion (1999ApJS..121....1M, Cat. III/235) catalog. The complete results from our survey, including the spectroscopic analysis of over 1100 DA white dwarfs, are presented. High signal-to-noise ratio optical spectra were obtained for each star and were subsequently analyzed using our standard spectroscopic technique where the observed Balmer line profiles are compared to synthetic spectra computed from the latest generation of model atmospheres appropriate for these stars. First, we present the spectroscopic content of our sample, which includes many misclassifications as well as several DAB, DAZ, and magnetic white dwarfs. Next, we look at how the new Stark broadening profiles affect the determination of the atmospheric parameters. When necessary, specific models and analysis techniques are used to derive the most accurate atmospheric parameters possible. In particular, we employ M dwarf templates to obtain better estimates of the atmospheric parameters for those white dwarfs that are in DA+dM binary systems.
- ID:
- ivo://CDS.VizieR/J/ApJ/647/303
- Title:
- Spectroscopic survey of hypervelocity stars
- Short Name:
- J/ApJ/647/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss our targeted search for hypervelocity stars (HVSs), stars traveling with velocities so extreme that dynamical ejection from a massive black hole is their only suggested origin. Our survey, now half-complete, has successfully identified a total of four probable HVSs plus a number of other unusual objects. Here we report the two most recently discovered HVSs: SDSS J110557.45+093439.5 and possibly SDSS J113312.12+010824, traveling with Galactic rest-frame velocities at least +508+/-12 and 418+/-10km/s, respectively.
