Markus Demleitner

THE PPMXL CATALOG OF POSITIONS AND PROPER MOTIONS ON THE ICRS. COMBINING USNO-B1.0 AND THE TWO MICRON ALL SKY SURVEY (2MASS)

USNO-B1.0 and the Two Micron All Sky Survey (2MASS) are the most widely used all-sky surveys. However, 2MASS has no proper motions at all, and USNO-B1.0 published only relative, not absolute (i.e., on the International Celestial Reference Frame (ICRS), proper motions. We performed a new determination of mean positions and proper motions on the ICRS system by combining USNO-B1.0 and 2MASS astrometry. This catalog is called PPMXL (VO access to the catalog is possible via http://vo.uni-hd.de/ppmxl), and it aims to be completed from the brightest stars down to about V ≈ 20 all sky. PPMXL contains about 900 million objects, some 410 million with 2MASS photometry, and is the largest collection of ICRS proper motions at present. As representative for the ICRS, we chose PPMX. The recently released UCAC3 could not be used because we found plate-dependent distortions in its proper motion system north of –20° declination. UCAC3 served as an intermediate system for δ ≤ –20°. The resulting typical individual mean errors of the proper motions range from 4 mas yr–1 to more than 10 mas yr–1 depending on observational history. The mean errors of positions at epoch 2000.0 are 80-120 mas, if 2MASS astrometry could be used, 150-300 mas else. We also give correction tables to convert USNO-B1.0 observations of, e.g., minor planets to the ICRS system.

CALIFA, the Calar Alto Legacy Integral Field Area survey

We present the Calar Alto Legacy Integral Field Area survey (CALIFA). CALIFAs main aim is to obtain spatially resolved spectroscopic information for ~600 galaxies of all Hubble types in the Local Universe (0.005< z <0.03). The survey has been designed to allow three key measurements to be made: (a) Two-dimensional maps of stellar populations (star formation histories, chemical elements); (b) The distribution of the excitation mechanism and element abundances of the ionized gas; and (c) Kinematic properties (velocity ?elds, velocity dispersion), both from emission and from absorption lines. To cover the full optical extension of the target galaxies (i.e. out to a 3sigma depth of ~23 mag/arcsec2), CALIFA uses the exceptionally large ?eld of view of the PPAK/PMAS IFU at the 3.5m telescope of the Calar Alto observatory. We use two grating setups, one covering the wavelength range between 3700 and 5000 AA at a spectral resolution R~1650, and the other covering 4300 to 7000 AA at R~850. The survey was allocated 210 dark nights, distributed in 6 semesters and starting in July 2010 and is carried out by the CALIFA collaboration, comprising ~70 astronomers from 8 di?erent countries. As a legacy survey, the fully reduced data will be made publically available, once their quality has been veri?ed. We showcase here early results obtained from the data taken so far (21 galaxies).

CALIFA, the Calar Alto Legacy Integral Field Area survey IV. Third public data release

We present a dynamical classification system for galaxies based on the shapes of their circular velocity curves (CVCs). We derive the CVCs of 40 SAURON and 42 CALIFA galaxies across Hubble sequence via a full line-of-sight integration as provided by solutions of the axisymmetric Jeans equations. We use Principal Component Analysis (PCA) applied to the circular curve shapes to find characteristic features and use a k-means classifier to separate circular curves into classes. This objective classification method identifies four different classes, which we name Slow-Rising (SR), Flat (F), Sharp-Peaked (SP) and Round-Peaked (RP) circular curves. SR-CVCs are mostly represented by late-type spiral galaxies (Scd-Sd) with no prominent spheroids in the central parts and slowly rising velocities; F-CVCs span almost all morphological types (E,S0,Sab,Sb-Sbc) with flat velocity profiles at almost all radii; SP-CVCs are represented by early-type and early-type spiral galaxies (E,S0,Sb-Sbc) with prominent spheroids and sharp peaks in the central velocities. RP-CVCs are represented by only two morphological types (E,Sa-Sab) with prominent spheroids, but RP-CVCs have much rounder peaks in the central velocities than SP-CVCs. RP-CVCs are typical for high-mass galaxies, while SR-CVCs are found for low-mass galaxies. Intermediate-mass galaxies usually have F-CVCs and SP-CVCs. Circular curve classification presents an alternative to typical morphological classification and may be more tightly linked to galaxy evolution.This paper describes the Third Public Data Release (DR3) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. Science-grade quality data for 667 galaxies are made public, including the 200 galaxies of the Second Public Data Release (DR2). Data were obtained with the integral-field spectrograph PMAS/PPak mounted on the 3.5m telescope at the Calar Alto Observatory. Three different spectral setups are available, i) a low-resolution V500 setup covering the wavelength range 3749-7500 AA (4240-7140 AA unvignetted) with a spectral resolution of 6.0 AA (FWHM), for 646 galaxies, ii) a medium-resolution V1200 setup covering the wavelength range 3650-4840 AA (3650-4620 AA unvignetted) with a spectral resolution of 2.3 AA (FWHM), for 484 galaxies, and iii) the combination of the cubes from both setups (called COMBO), with a spectral resolution of 6.0 AA and a wavelength range between 3700-7500 AA (3700-7140 AA unvignetted), for 446 galaxies. The Main Sample, selected and observed according to the CALIFA survey strategy covers a redshift range between 0.005 and 0.03, spans the color-magnitude diagram and probes a wide range of stellar mass, ionization conditions, and morphological types. The Extension Sample covers several types of galaxies that are rare in the overall galaxy population and therefore not numerous or absent in the CALIFA Main Sample. All the cubes in the data release were processed using the latest pipeline, which includes improved versions of the calibration frames and an even further improved im- age reconstruction quality. In total, the third data release contains 1576 datacubes, including ~1.5 million independent spectra. It is available at this http URL

Prediction of astrometric microlensing events during the Gaia mission

We identify stars with large proper motions that are potential candidates for the astrometric microlensing effect during the Gaia mission i.e. between 2012 and 2019. The effect allows a precise measurement of the mass of a single star that is acting as a lens. We construct a candidate list by combining information from several input catalogs including PPMXL, LSPM, PPMX, OGLEBG, and UCAC3. The selection of the microlensing candidates includes the verification of their proper motions as well as the calculation of the centroid shift of the source resulting from the astrometric microlensing effect. The assembled microlensing catalog comprises 1118 candidates for the years 2012 to 2019. Our analysis demonstrates that 96% of the (high) proper motions of these candidates are erroneous. We are thus left with 43 confirmed candidates for astrometric microlensing during the expected Gaia mission. For most of them the light centroid shift is below ∼100 μas (assuming a dark lens) or the astrometric deviation is considerably reduced by the brightness of the lens. Due to this the astrometric microlensing effect can potentially be measured for nine candidates that have a centroid shift between 100 and 4000 μas. For two of these astrometric microlensing candidates we predict a strong centroid shift of about 1000 and 4000 μas, respectively, that should be observable over a period of a few months up to a few years with the Gaia mission.

Stellar laboratories - VI. New Mo iv–vii oscillator strengths and the molybdenum abundance in the hot white dwarfs G191−B2B and RE 0503−289

For the spectral analysis of high-resolution and high-signal-to-noise (S/N) spectra of hot stars, state-of-the-art non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These are strongly dependent on the reliability of the atomic data that is used for their calculation. To identify molybdenum lines in the ultraviolet (UV) spectra of the DA-type white dwarf G191-B2B and the DO-type white dwarf RE0503-289 and to determine their photospheric Mo abundances, newly calculated Mo IV - VII oscillator strengths are used. We identified twelve Mo V and nine Mo VI lines in the UV spectrum of RE0503-289 and measured a photospheric Mo abundance of 1.2 - 3.0 x 10**-4 (mass fraction, 22500 - 56400 times the solar abundance). In addition, from the As V and Sn IV resonance lines, we measured mass fractions of arsenic (0.5 - 1.3 x 10**-5, about 300 - 1200 times solar) and tin (1.3 - 3.2 x 10**-4, about 14300 35200 times solar). For G191-B2B, upper limits were determined for the abundances of Mo (5.3 x 10**-7, 100 times solar) and, in addition, for Kr (1.1 x 10**-6, 10 times solar) and Xe (1.7 x 10**-7, 10 times solar). The arsenic abundance was determined (2.3 - 5.9 x 10**-7, about 21 - 53 times solar). A new, registered German Astrophysical Virtual Observatory (GAVO) service, TOSS, has been constructed to provide weighted oscillator strengths and transition probabilities. Reliable measurements and calculations of atomic data are a prerequisite for stellar-atmosphere modeling. Observed Mo V - VI line profiles in the UV spectrum of the white dwarf RE0503-289 were well reproduced with our newly calculated oscillator strengths. For the first time, this allowed to determine the photospheric Mo abundance in a white dwarf.

Stellar laboratories. VII. New Kr IV - VII oscillator strengths and their validation in the hot hydrogen-deficient DO-type white dwarf RE0503-289

Context. For the spectral analysis of high-resolution and high signal-to-noise (S/N) spectra of hot stars, state-of-the-art non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These are strongly dependent on the reliability of the atomic data that is used for their calculation. Aims. New Kr iv–vii oscillator strengths for a large number of lines enable us to construct more detailed model atoms for our NLTE model-atmosphere calculations. This enables us to search for additional Kr lines in observed spectra and to improve Kr abundance determinations. Methods. We calculated Kr iv–vii oscillator strengths to consider radiative and collisional bound-bound transitions in detail in our NLTE stellar-atmosphere models for the analysis of Kr lines that are exhibited in high-resolution and high S/N ultraviolet (UV) observations of the hot white dwarf RE 0503−289. Results. We reanalyzed the effective temperature and surface gravity and determined T eff = 70000 ± 2000 K and log  ( g / cm s -2 ) = 7.5 ± 0.1. We newly identified ten Kr v lines and one Kr vi line in the spectrum of RE 0503−289. We measured a Kr abundance of −3.3 ± 0.3 (logarithmic mass fraction). We discovered that the interstellar absorption toward RE 0503−289 has a multi-velocity structure within a radial-velocity interval of −40 km s -1 v rad -1 . Conclusions. Reliable measurements and calculations of atomic data are a prerequisite for state-of-the-art NLTE stellar-atmosphere modeling. Observed Kr v–vii line profiles in the UV spectrum of the white dwarf RE 0503−289 were simultaneously well reproduced with our newly calculated oscillator strengths.

Stellar laboratories. VIII. New Zr IV - VII, Xe IV - V, and Xe VII oscillator strengths and the Al, Zr and Xe abundances in the hot white dwarfs G191-B2B and RE0503-289

Context. For the spectral analysis of high-resolution and high-signal-to-noise spectra of hot stars, state-of-the-art non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These are strongly dependent on the reliability of the atomic data that is used for their calculation. Aims. To search for zirconium and xenon lines in the ultraviolet (UV) spectra of G191−B2B and RE 0503−289, new Zr iv–vii, Xe iv–v, and Xe vii oscillator strengths were calculated. This allows, for the first time, determination of the Zr abundance in white dwarf (WD) stars and improvement of the Xe abundance determinations. Methods. We calculated Zr iv–vii, Xe iv–v, and Xe vii oscillator strengths to consider radiative and collisional bound-bound transitions of Zr and Xe in our NLTE stellar-atmosphere models for the analysis of their lines exhibited in UV observations of the hot WDs G191−B2B and RE 0503−289. Results. We identified one new Zr iv, 14 new Zr v, and ten new Zr vi lines in the spectrum of RE 0503−289. Zr was detected for the first time in a WD. We measured a Zr abundance of −3.5 ± 0.2 (logarithmic mass fraction, approx. 11 500 times solar). We identified five new Xe vi lines and determined a Xe abundance of −3.9 ± 0.2 (approx. 7500 times solar). We determined a preliminary photospheric Al abundance of −4.3 ± 0.2 (solar) in RE 0503−289. In the spectra of G191−B2B, no Zr line was identified. The strongest Zr iv line (1598.948 A) in our model gave an upper limit of −5.6 ± 0.3 (approx. 100 times solar). No Xe line was identified in the UV spectrum of G191−B2B and we confirmed the previously determined upper limit of −6.8 ± 0.3 (ten times solar). Conclusions. Precise measurements and calculations of atomic data are a prerequisite for advanced NLTE stellar-atmosphere modeling. Observed Zr iv–vi and Xe vi-vii line profiles in the UV spectrum of RE 0503−289 were simultaneously well reproduced with our newly calculated oscillator strengths.

Stellar laboratories : IX. New Se v, Sr iv–vii, Te vi, and I vi oscillator strengths and the Se, Sr, Te, and I abundances in the hot white dwarfs G191−B2B and RE 0503−289⋆⋆⋆⋆⋆⋆

To analyze spectra of hot stars, advanced non-local thermodynamic equilibrium (NLTE) model-atmosphere techniques are mandatory. Reliable atomic data is for the calculation of such model atmospheres. We aim to calculate new Sr IV - VII oscillator strengths to identify for the first time Sr spectral lines in hot white dwarf (WD) stars and to determine the photospheric Sr abundances. o measure the abundances of Se, Te, and I in hot WDs, we aim to compute new Se V, Te VI, and I VI oscillator strengths. To consider radiative and collisional bound-bound transitions of Se V, Sr IV - VII, Te VI, and I VI in our NLTE atmosphere models, we calculated oscillator strengths for these ions. We newly identified four Se V, 23 Sr V, 1 Te VI, and three I VI lines in the ultraviolet (UV) spectrum of RE0503-289. We measured a photospheric Sr abundance of 6.5 +3.8/-2.4 x 10**-4 (mass fraction, 9500 - 23800 times solar). We determined the abundances of Se (1.6 +0.9/-0.6 x 10**-3, 8000 - 20000), Te (2.5 +1.5/-0.9 x 10**-4, 11000 - 28000), and I (1.4 +0.8/-0.5 x 10**-5, 2700 - 6700). No Se, Sr, Te, and I line was found in the UV spectra of G191-B2B and we could determine only upper abundance limits of approximately 100 times solar. All identified Se V, Sr V, Te VI, and I VI lines in the UV spectrum of RE0503-289 were simultaneously well reproduced with our newly calculated oscillator strengths.

A Gaia DR2 Mock Stellar Catalog

We present a mock catalog of Milky Way stars, matching in volume and depth the content of the Gaia data release 2 (GDR2). We generated our catalog using Galaxia, a tool to sample stars from a Besancon Galactic model, together with a realistic 3D dust extinction map. The catalog mimicks the complete GDR2 data model and contains most of the entries in the Gaia source catalog: 5-parameter astrometry, 3-band photometry, radial velocities, stellar parameters, and associated scaled nominal uncertainty estimates. In addition, we supplemented the catalog with extinctions and photometry for non-Gaia bands. This catalog can be used to prepare GDR2 queries in a realistic runtime environment, and it can serve as a Galactic model against which to compare the actual GDR2 data in the space of observables. The catalog is hosted through the virtual observatory GAVOs Heidelberg data center service and thus can be queried using ADQL as for GDR2 data.

Ongoing astrometric microlensing events of two nearby stars

Context. Astrometric microlensing is an excellent tool to determine the mass of a stellar object. By measuring the astrometric shift of a background source star in combination with precise predictions of its unlensed position and of the lens position, gravitational lensing allows to determine the mass of the lensing star with a precision of 1 percent, independent of any prior knowledge. Aims. Making use of the recently published Gaia Data Release 2 (Gaia DR2) we predict astrometric microlensing events by foreground stars of high proper motion passing by a background star in the coming years. Methods. We compile a list of ~148.000 high-proper-motion stars within Gaia DR2 with