- ID:
- ivo://CDS.VizieR/J/AJ/158/147
- Title:
- Spectrophotometric parallaxes with linear models
- Short Name:
- J/AJ/158/147
- Date:
- 07 Jan 2022 11:19:14
- Publisher:
- CDS
- Description:
- With contemporary infrared spectroscopic surveys like APO Galactic Evolution Experiment (APOGEE), red-giant stars can be observed to distances and extinctions at which Gaia parallaxes are not highly informative. Yet the combination of effective temperature, surface gravity, composition, and age-all accessible through spectroscopy - determines a giant's luminosity. Therefore spectroscopy plus photometry should enable precise spectrophotometric distance estimates. Here we use the overlap of APOGEE, Gaia, the Two Micron All Sky Survey (2MASS), and the Wide-field Infrared Survey Explorer (WISE) to train a data-driven model to predict parallaxes for red-giant branch stars with 0<logg=<2.2 (more luminous than the red clump). We employ (the exponentiation of) a linear function of APOGEE spectral pixel intensities and multiband photometry to predict parallax spectrophotometrically. The model training involves no logarithms or inverses of the Gaia parallaxes, and needs no cut on the Gaia parallax signal-to-noise ratio. It includes an L1 regularization to zero out the contributions of uninformative pixels. The training is performed with leave-out subsamples such that no star's astrometry is used even indirectly in its spectrophotometric parallax estimate. The model implicitly performs a reddening and extinction correction in its parallax prediction, without any explicit dust model. We assign to each star in the sample a new spectrophotometric parallax estimate; these parallaxes have uncertainties of less than 15%, depending on data quality, which is more precise than the Gaia parallax for the vast majority of targets, and certainly any stars more than a few kiloparsec distance. We obtain 10% distance estimates out to heliocentric distances of 20 kpc, and make global maps of the Milky Way's disk.
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Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/656/168
- Title:
- Spectrophotometry in NGC 5253
- Short Name:
- J/ApJ/656/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present echelle spectrophotometry of the blue compact dwarf galaxy NGC 5253 obtained with the VLT UVES. We have measured the intensities of a large number of permitted and forbidden emission lines in four zones of the central part of the galaxy. We detect faint CII and OII recombination lines, the first time that these are unambiguously detected in a dwarf starburst galaxy. The physical conditions of the ionized gas have been derived using a large number of different line intensity ratios.
- ID:
- ivo://CDS.VizieR/J/PAZh/23/409
- Title:
- Spectrophotometry of Mrk 509
- Short Name:
- J/PAZh/23/409
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variability of the continuum, H{beta}, H{gamma} and HeII(4686{AA}) fluxes of the Seyfert I galaxy Mrk 509 is studied using spectra obtained on the 2.6-m telescope of the Crimean Astrophysical observatory from 1971-1993. All the measurements of fluxes are in the relative units normalized to the flux of [OIII](5007{AA}) taken equal to 100. The flux in the line [OIII](5007{AA}) is estimated in the interval of (5.7-7.6)*10^-13^erg/cm^2^/s=(5.7-7.6)*10^-16^W/m2. The variability amplitude in the continuum is higher than in the hydrogen lines.
- ID:
- ivo://CDS.VizieR/J/ApJS/164/81
- Title:
- Spectrophotometry of nearby galaxies
- Short Name:
- J/ApJS/164/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present integrated optical spectrophotometry for a sample of 417 nearby galaxies. Our observations consist of spatially integrated, S/N=10-100 spectroscopy between 3600 and 6900{AA} at ~8{AA} FWHM resolution. In addition, we present nuclear (2.5"x2.5") spectroscopy for 153 of these objects. Our sample targets a diverse range of galaxy types, including starbursts, peculiar galaxies, interacting/merging systems, dusty, infrared-luminous galaxies, and a significant number of normal galaxies. We use population synthesis to model and subtract the stellar continuum underlying the nebular emission lines. This technique results in emission-line measurements reliably corrected for stellar absorption. Here we present the integrated and nuclear spectra, the nebular emission-line fluxes and equivalent widths, and a comprehensive compilation of ancillary data available in the literature for our sample.
- ID:
- ivo://CDS.VizieR/J/A+A/417/499
- Title:
- Spectrophotometry of Virgo cluster galaxies
- Short Name:
- J/A+A/417/499
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Drift-scan mode (3600-6800{AA}) spectra with 500<R<1000 resolution are presented for 333 galaxies members to nearby clusters, covering the whole Hubble sequence. The majority (225) were obtained for galaxies in the Virgo cluster where a completeness of 36%, if all Hubble types are considered, and of 5 %, restricting to late-types, was reached at mp<=16. Our data can be therefore considered representative of the integrated spectral properties of giant and dwarf galaxies in this cluster. Intensities and equivalent widths (EWs) are derived for the principal lines, both in emission and in absorption. Deblending of the underlying absorption from emission was achieved in most cases.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A113
- Title:
- Spectropolarimetric survey of white dwarfs
- Short Name:
- J/A+A/618/A113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our knowledge of the magnetism in white dwarfs is based on an observational dataset that is biased in favour of stars with very strong magnetic fields. Most of the field measurements available in the literature have a relatively low sensitivity, while current instruments allow us to detect magnetic fields of white dwarfs with sub-kG precision. With the aim of obtaining a more complete view of the incidence of magnetic fields in degenerate stars, we have started a long-term campaign of high-precision spectropolarimetric observations of white dwarfs. Here we report the results obtained so far with the low-resolution FORS2 instrument of the ESO VLT and the medium-resolution ISIS instrument of the WHT. We have considered a sample of 48 stars, of which five are known magnetic or suspected magnetic stars, and obtained new longitudinal magnetic field measurements with a mean uncertainty of about 0.6kG. Overall, in the course of our survey (the results of which have been partially published in papers devoted to individual stars) we have discovered one new weak-field magnetic white dwarf, confirmed the magnetic nature of another, found that a suspected magnetic star is not magnetic, and suggested two new candidate magnetic white dwarfs. Even combined with data previously obtained in the literature, our sample is not sufficient yet to reach any final conclusions about the actual incidence of very weak magnetic fields in white dwarfs, but we have set the basis to achieve a homogeneous survey of an unbiased sample of white dwarfs. As a by-product, our survey has also enabled us to carry out a detailed characterisation of the ISIS and the FORS2 instruments for the detection of extremely weak magnetic fields in white dwarfs, and in particular to relate the signal-to-noise ratio to measurement uncertainty for white dwarfs of different spectral types. This study will help the optimisation of future observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/2879
- Title:
- Spectropolarimetry of active galaxy 3C 390.3
- Short Name:
- J/MNRAS/448/2879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Here we present the spectropolarimetric observations of the radio-loud active galaxy 3C 390.3 in the period 2009-2014 (24 epochs). The galaxy has been observed with the 6-m telescope of Special Astrophysical Observatory of the Russian Academy of Science (SAO RAS) using the Spectral Camera with Optical Reducer for Photometric and Interferometric Observations (SCORPIO) spectropolarimeter. We explore the variability and lags in the polarized light of the continuum and broad H{alpha} line. We give the Stokes parameters Q, U, degree of linear polarization P and the position angle of the polarization plane, {phi}, for 24 epochs. We find a small lag (10-40 d) between the unpolarized and polarized continuum that is significantly smaller than the estimated lags for the unpolarized broad emission lines (lag(H{alpha}) ~138-186 and lag(H{beta}) ~60-79 d). This shows that the region of the variable polarized continuum is significantly smaller than the broad line region, indicating that a part of the polarized continuum is coming from the jet. The lag of the polarized light in the H{alpha} line (89-156 d) indicates an additional component to the disc one that has an outflowing velocity of ~-1200 km/s. This region seems to depolarize the polarized broad H{alpha} line emitted from the disc and scattered in the inner part of the torus.
- ID:
- ivo://CDS.VizieR/J/AJ/147/16
- Title:
- Spectroscocpy of planetary nebulae in M31
- Short Name:
- J/AJ/147/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have developed a method to identify planetary nebula (PN) candidates in imaging data of the Sloan Digital Sky Survey (SDSS). This method exploits the SDSS's five-band sampling of emission lines in PN spectra, which results in a color signature distinct from that of other sources. Selection criteria based on this signature can be applied to nearby galaxies in which PNe appear as point sources. We applied these criteria to the whole area of M31 as scanned by the SDSS, selecting 167 PN candidates that are located in the outer regions of M31. The spectra of 80 selected candidates were then observed with the 2.2m telescope at Calar Alto Observatory. These observations and cross-checks with literature data show that our method has a selection rate efficiency of about 90%, but the efficiency is different for the different groups of PN candidates. In the outer regions of M31, PNe trace different well-known morphological features like the Northern Spur, the NGC 205 Loop, the G1 Clump, etc. In general, the distribution of PNe in the outer region 8<R<20kpc along the minor axis shows the "extended disk"-a rotationally supported low surface brightness structure with an exponential scale length of 3.21+/-0.14kpc and a total mass of ~10^10^M_{sun}_, which is equivalent to the mass of M33. We report the discovery of three PN candidates with projected locations in the center of Andromeda NE, a very low surface brightness giant stellar structure in the outer halo of M31. Two of the PNe were spectroscopically confirmed as genuine PNe. These two PNe are located at projected distances along the major axis of ~48Kpc and ~41Kpc from the center of M31 and are the most distant PNe in M31 found up to now. With the new PN data at hand we see the obvious kinematic connection between the continuation of the Giant Stream and the Northern Spur. We suggest that 20%-30% of the stars in the Northern Spur area may belong to the Giant Stream. In our data we also see a possible kinematic connection between the Giant Stream and PNe in Andromeda NE, suggesting that Andromeda NE could be the core or remnant of the Giant Stream. Using PN data we estimate the total mass of the Giant Stream progenitor to be {approx}10^9^M_{sun}_. About 90% of its stars appear to have been lost during the interaction with M31.
- ID:
- ivo://CDS.VizieR/J/ApJ/839/42
- Title:
- Spectrosc. of the circumstellar gas of WD1145+017
- Short Name:
- J/ApJ/839/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the recent discovery of transiting planetary material around WD1145+017, a critical target has been identified that links the evolution of planetary systems with debris disks and their accretion onto the star. We present a series of observations, five epochs over a year, taken with Keck and the VLT, which for the first time show variability of circumstellar absorption in the gas disk surrounding WD1145+017 on timescales of minutes to months. Circumstellar absorption is measured in more than 250 lines of 14 ions among 10 different elements associated with planetary composition, e.g., O, Mg, Ca, Ti, Cr, Mn, Fe, and Ni. Broad circumstellar gas absorption with a velocity spread of 225km/s is detected, but over the course of a year blueshifted absorption disappears, while redshifted absorption systematically increases. A correlation of equivalent width and oscillator strength indicates that the gas is not highly optically thick (median {tau}~2). We discuss simple models of an eccentric disk coupled with magnetospheric accretion to explain the basic observed characteristics of these high-resolution and high signal- to-noise observations. Variability is detected on timescales of minutes in the two most recent observations, showing a loss of redshifted absorption for tens of minutes, coincident with major transit events and consistent with gas hidden behind opaque transiting material. This system currently presents a unique opportunity to learn how the gas causing the spectroscopic, circumstellar absorption is associated with the ongoing accretion evidenced by photospheric contamination, as well as the transiting planetary material detected in photometric observations.
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