Papers by Matthias Steinmetz
Serdica Journal of Computing
We present the Potsdam photographic plate library at the Leibniz Institute for Astrophysics Potsd... more We present the Potsdam photographic plate library at the Leibniz Institute for Astrophysics Potsdam. It includes plate archives, data from plate index catalogues and extracts from astronomical logbooks, as well as digitized plate images and interfaces for accessing all the available information. The plate index catalogues and the digitized images of the Potsdam astronomical photographic plates are prepared according to the standards of the Wide-Field Plate Database and German Astrophysical Virtual Observatory. The high-resolution digitization of the plates (in standardized FITS file format), the low-resolution plate previews (in TIFF and JPEG file format), as well as suitable digitization of the catalogues, logbooks, and relevant scientific research papers (in JPEG and TIFF) are made using commercial flatbed scanners.
s *********************************************************************************** THE WIDE-FI... more s *********************************************************************************** THE WIDE-FIELD PLATE DATABASE: DEVELOPMENT AND ACCESS VIA INTERNET ∗ Milcho Tsvetkov e-mail: [email protected] ACM Computing Classification System (1998): J.2.
We present the Potsdam photographic plate library at the Leibniz Institute for Astrophysics Potsd... more We present the Potsdam photographic plate library at the Leibniz Institute for Astrophysics Potsdam. It includes plate archives, data from plate index catalogues and extracts from astronomical logbooks, as well as digitized plate images and interfaces for accessing all the available information. The plate index catalogues and the digitized images of the Potsdam astronomical photographic plates are prepared according to the standards of the Wide-Field Plate Database and German Astrophysical Virtual Observatory. The high-resolution digitization of the plates (in standardized FITS file format), the low-resolution plate previews (in TIFF and JPEG file format), as well as suitable digitization of the catalogues, logbooks, and relevant scientific research papers (in JPEG and TIFF) are made using commercial flatbed scanners. ACM Computing Classification System (1998): J.2.
Research Notes of the AAS, 2018
The Radial Velocity Experiment (Steinmetz et al. (2006)) is a massive spectroscopic campaign of s... more The Radial Velocity Experiment (Steinmetz et al. (2006)) is a massive spectroscopic campaign of some 460 000 stars in the southern hemisphere. RAVE spectra were taken with the 6dF multi-object spectrograph on the 1.2m UK Schmidt telescope of the Australian Astronomical Observatory (formerly Anglo-Australian Observatory). RAVE spectra are taken at a resolution of R ≈ 7500 in the IR Calcium triplet region (8410-8795Å). Observations for RAVE were taken between April 2003 and April 2013. On 25 April 2018, the 2nd data release of the ESA mission Gaia was published (Gaia Collaboration et al. (2018)), featuring radial velocities for some 7 million targets. The Radial Velocity Spectrometer (RVS) of Gaia also operates in the Ca triplet region, though at a somewhat higher resolution of R = 11000. This research note presents a comparison of radial velocities between the most recent data release of RAVE (Kunder et al. (2017)) with Gaia DR2. RAVE DR5 and Gaia DR2 have 450587 stars in common. In particular we would like to shed light on a small subset of joint targets (707 stars) that exhibit a constant velocity offset of +105 km s −1 (see also Reddy, D. & Reddy, B. (2018)) or −76 km s −1 , respectively. Since RAVE provided the largest subset of targets for the Gaia pipeline verification, the two data sets are not fully independent.
The Astronomical Journal, 2020
We present part 2 of the 6th and final Data Release (DR6 or FDR) of the Radial Velocity Experimen... more We present part 2 of the 6th and final Data Release (DR6 or FDR) of the Radial Velocity Experiment (Rave), a magnitude-limited (9 < I < 12) spectroscopic survey of Galactic stars randomly selected in the southern hemisphere. The Rave mediumresolution spectra (R ∼ 7500) cover the Ca-triplet region (8410 − 8795Å) and span the complete time frame from the start of Rave observations on 12 April 2003 to their completion on 4 April 2013. In the second of two publications, we present the data products derived from 518 387 observations of 451 783 unique stars using a suite of advanced reduction pipelines focussing on stellar atmospheric parameters, in particular purely spectroscopicallyderived stellar atmospheric parameters (T eff , log g, and the overall metallicity), enhanced stellar parameters inferred via a Bayesian pipeline using Gaia DR2 astrometric priors, and asteroseismically calibrated stellar parametersfor giant stars based on asteroseismic observations for 699 K2 stars. In addition, we provide abundances of the elements Fe, Al, and Ni, as well as an overall [α/Fe] ratio obtained using a new pipeline based on the GAUGUIN optimization method that is able to deal with variable signal-to-noise ratios.The Rave DR6 catalogs are cross matched with relevant astrometric and photometric catalogs, and are complemented by orbital Rave DR6-II.: stellar parameters and abundances 3 parameters and effective temperatures based on the infrared flux method. The data can be accessed via the Rave Web site a) or the Vizier database.
Proceedings of the International Astronomical Union, 2017
The 5th RAVE data release is based on 520,781 spectra (R ≈ 7500 in the CaT region at 8410 - 8795Å... more The 5th RAVE data release is based on 520,781 spectra (R ≈ 7500 in the CaT region at 8410 - 8795Å) of 457,588 unique stars. RAVE DR5 provides radial velocities, stellar parameters and individual abundances for up to seven elements and distances found using isochrones for a considerable subset of these objects. In particular, RAVE DR5 has 255,922 stellar observations that also have parallaxes and proper motions from the Tycho-Gaia astrometric solution (TGAS) in Gaia DR1. The combination of RAVE and TGAS thus provides the currently largest overlap of spectroscopic and space-based astrometric data and thus can serve as a formidable preview of what Gaia is going to deliver in coming data releases. Basic properties of the RAVE+TGAS survey and its derived data products are presented as well as first applications w.r.t wave-like patterns in the disk structure. An outlook to the 6th RAVE data release is given.
Monthly Notices of the Royal Astronomical Society, 2016
We present evidence from the RAdial Velocity Experiment (RAVE) survey of chemically separated, ki... more We present evidence from the RAdial Velocity Experiment (RAVE) survey of chemically separated, kinematically distinct disc components in the solar neighbourhood. We apply probabilistic chemical selection criteria to separate our sample into α-low ('thin disc') and α-high ('thick disc') sequences. Using newly derived distances, which will be utilized in the upcoming RAVE DR5, we explore the kinematic trends as a function of metallicity for each of the disc components. For our α-low disc, we find a negative trend in the mean rotational velocity (V φ) as a function of iron abundance ([Fe/H]). We measure a positive gradient ∂V φ /∂[Fe/H] for the α-high disc, consistent with results from high-resolution surveys. We also find differences between the α-low and α-high discs in all three components of velocity dispersion. We discuss the implications of an α-low, metal-rich population originating from the inner Galaxy, where the orbits of these stars have been significantly altered by radial mixing mechanisms in order to bring them into the solar neighbourhood. The probabilistic separation we propose can be extended to other data sets for which the accuracy in [α/Fe] is not sufficient to disentangle the chemical disc components a priori. For such data sets which will also have significant overlap with Gaia DR1, we can therefore make full use of the improved parallax and proper motion data as it becomes available to investigate kinematic trends in these chemical disc components.
Proceedings of the International Astronomical Union, 2015
Throughout the past decade, significant advances have been made in the size and scope of large-sc... more Throughout the past decade, significant advances have been made in the size and scope of large-scale spectroscopic surveys, allowing for the opportunity to study in-depth the formation history of the Milky Way. Using the fourth data release of the RAdial Velocity Experiment (RAVE), we study the age-metallicity-velocity space of ~ 100,000 FGK stars in the extended solar neighborhood in order to explore evolutionary processes. Combining these three parameters, we better constrain our understanding of these interconnected, fundamental processes.
The Astrophysical Journal, 2015
The version presented here may differ from the published version or from the version of the recor... more The version presented here may differ from the published version or from the version of the record. Please see the repository URL above for details on accessing the published version and note that access may require a subscription.
SPIE Proceedings, 2010
The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field ... more The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph currently in manufacturing, assembly and integration phase. MUSE has a field of 1x1 arcmin² sampled at 0.2x0.2 arcsec² and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The instrument is a large assembly of 24 identical high performance integral field units, each one composed of an advanced image slicer, a spectrograph and a 4kx4k detector. In this paper we review the progress of the manufacturing and report the performance achieved with the first integral field unit.
Science (New York, N.Y.), Jan 15, 2014
The diffuse interstellar bands (DIBs) are absorption lines observed in visual and near-infrared s... more The diffuse interstellar bands (DIBs) are absorption lines observed in visual and near-infrared spectra of stars. Understanding their origin in the interstellar medium is one of the oldest problems in astronomical spectroscopy, as DIBs have been known since 1922. In a completely new approach to understanding DIBs, we combined information from nearly 500,000 stellar spectra obtained by the massive spectroscopic survey RAVE (Radial Velocity Experiment) to produce the first pseudo-three-dimensional map of the strength of the DIB at 8620 angstroms covering the nearest 3 kiloparsecs from the Sun, and show that it follows our independently constructed spatial distribution of extinction by interstellar dust along the Galactic plane. Despite having a similar distribution in the Galactic plane, the DIB 8620 carrier has a significantly larger vertical scale height than the dust. Even if one DIB may not represent the general DIB population, our observations outline the future direction of DIB ...
The Astronomical Journal, 2009
The Sloan Extension for Galactic Understanding and Exploration (SEGUE) survey obtained ≈ 240,000 ... more The Sloan Extension for Galactic Understanding and Exploration (SEGUE) survey obtained ≈ 240,000 moderate resolution (R ∼ 1800) spectra from 3900Å to 9000Å of fainter Milky Way stars (14.0 < g < 20.3) of a wide variety of spectral types, both main-sequence and evolved objects, with the goal of studying the kinematics and populations of our Galaxy and its halo. The spectra are clustered in 212 regions spaced over three-quarters of the sky. Radial velocity accuracies for stars are σ(RV) ∼ 4 km s −1 at g < 18, degrading to σ(RV) ∼ 15 km s −1 at g ∼ 20. For stars with signal-to-noise ratio > 10 per resolution element, stellar atmospheric parameters are estimated, including metallicity, surface gravity, and effective temperature. SEGUE obtained 3500deg 2 of additional ugriz imaging (primarily at low Galactic latitudes) providing precise multicolor photometry (σ(g, r, i) ∼ 2%), (σ(u, z) ∼ 3%) and astrometry (≈ 0.1 ′′) for spectroscopic target selection. The stellar spectra, imaging data, and derived parameter catalogs for this survey are publicly available as part of Sloan Digital Sky Survey Data Release 7.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012
When an ultra-high energy neutrino or cosmic ray strikes the Lunar surface a radio-frequency puls... more When an ultra-high energy neutrino or cosmic ray strikes the Lunar surface a radio-frequency pulse is emitted. We plan to use the LOFAR radio telescope to detect these pulses. In this work we propose an efficient trigger implementation for LOFAR optimized for the observation of short radio pulses.
Nature, 2009
Virtually all massive galaxies, including our own, host central black holes ranging in mass from ... more Virtually all massive galaxies, including our own, host central black holes ranging in mass from millions to billions of solar masses. The growth of these black holes releases vast amounts of energy that powers quasars and other weaker active galactic nuclei. A tiny fraction of this energy, if absorbed by the host galaxy, could halt star formation by heating and ejecting ambient gas. A central question in galaxy evolution is the degree to which this process has caused the decline of star formation in large elliptical galaxies, which typically have little cold gas and few young stars, unlike spiral galaxies. Galaxies come in two basic types: ‗football-shaped' ellipticals and ‗disk-shaped' spirals (Fig. 1). Spirals contain plenty of cold gas, which forms stars, whereas the gas in ellipticals is too hot to form stars. Thus, ellipticals lack the young blue stars that are usually seen in spirals, and are generally quite red. Spirals also have central bulges structurally resembling miniature ellipticals. Owing to this similarity, we use the term ‗bulges' for bulges within spirals and for ellipticals indiscriminately. Each bulge contains a central black hole, whose mass is proportional to the bulge stellar mass 1-5 , M BH ≈ 0.001M bulge. Black holes and bulges also formed at about the same epoch in the lifetime of the Universe 6,7. These observations imply that the formation of black holes and the formation of bulges are closely linked. Matter falling onto a black hole releases a huge amount of energy 8 , of the order of 10% of the rest mass energy, E = mc 2 , mainly in the form of photons but also in the form of radio-luminous jets of charged particles 9,10. Even a tiny fraction (<1%) of the energy released within each bulge could heat and blow away its entire gas content, thus explaining the lack of star formation in bulges. The theorist's goal is to understand these observations in a cosmological context. In the standard picture 11-13 , most of the Universe is composed of dark matter, whose nature is unknown. Protons, electrons and neutrons, which compose gas and stars, make up the rest. They interact with dark matter purely through gravity, which determines the evolution of the Universe on large scales. The Universe emerged from the Big Bang with small inhomogeneities. These eventually grew into lumps, called haloes, by attracting surrounding matter gravitationally (Fig. 2). The competition between radiative cooling and gravitational heating determines the fate of gas in these haloes 14-16. In low-mass haloes, cooling dominates. Galaxies grow through the accretion of gas that falls to the centre in cold flows 17,18 , settles into disks 19 (but see refs 20, 21), and forms stars. However, when the halo mass grows above a critical value of about 10 12 solar masses 18 , heating dominates, and the gas no longer accretes onto galaxies. Halo mergers form large haloes that contain tens or even hundreds of galaxies, called groups or clusters, respectively. Galaxy mergers within haloes transform disks into bulges 22 and are the only opportunity for galaxies to grow after they have ceased to accrete gas. In mergers of galaxies that are still accreting gas, the gas falls to the centre, triggers starbursts, and is often observed to feed the rapid growth of black holes 23,24 , although, observationally, the connection between active galactic nuclei (AGN) and mergers remains controversial 25-27. Black holes respond to this fuelling by feeding energy back to the surrounding gas. This energy produces winds 28-33 , which may accelerate the star formation rate by compressing the gas 34. In the most dramatic scenario, all the gas is blown away, so black hole growth and star formation suddenly terminate 35-39. Computer simulations suggest that this ‗quenching' is necessary to explain why ellipticals are red 40,41. The chemical composition
Monthly Notices of the Royal Astronomical Society, 2011
We study the eccentricity distribution of a thick-disc sample of stars (defined as those with V y... more We study the eccentricity distribution of a thick-disc sample of stars (defined as those with V y > 50 km s −1 and 1 < |z|/kpc < 3) observed in the Radial Velocity Experiment (RAVE). We compare this distribution with those obtained in four simulations of galaxy formation taken from the literature as compiled by Sales et al. Each simulation emphasizes different scenarios for the origin of such stars (satellite accretion, heating of a pre-existing thin disc during a merger, radial migration, and gas-rich mergers). We find that the observed distribution peaks at low eccentricities and falls off smoothly and rather steeply to high eccentricities. This finding is fairly robust to changes in distances and to plausible assumptions about thin-disc contamination. Our results favour models where the majority of stars formed in the Galaxy itself on orbits of modest eccentricity and disfavour the pure satellite accretion case. A gas-rich merger origin where most of the stars form 'in situ' appears to be the most consistent with our data.
Monthly Notices of the Royal Astronomical Society, 2013
Probability density functions (pdfs) are determined from new stellar parameters for the distance ... more Probability density functions (pdfs) are determined from new stellar parameters for the distance moduli of stars for which the RAdial Velocity Experiment (RAVE) has obtained spectra with S/N ≥ 10. Single-Gaussian fits to the pdf in distance modulus suffice for roughly half the stars, with most of the other half having satisfactory two-Gaussian representations. As expected, early-type stars rarely require more than one Gaussian. The expectation value of distance is larger than the distance implied by the expectation of distance modulus; the latter is itself larger than the distance implied by the expectation value of the parallax. Our parallaxes of Hipparcos stars agree well with the values measured by Hipparcos, so the expectation of parallax is the most reliable distance indicator. The latter are improved by taking extinction into account. The effective temperature-absolute magnitude diagram of our stars is significantly improved when these pdfs are used to make the diagram. We use the method of kinematic corrections devised by Schönrich, Binney and Asplund to check for systematic errors for general stars and confirm that the most reliable distance indicator is the expectation of parallax. For cool dwarfs and low-gravity giants, tends to be larger than the true distance by up to 30 per cent. The most satisfactory distances are for dwarfs hotter than 5500 K. We compare our distances to stars in 13 open clusters with cluster distances from the literature and find excellent agreement for the dwarfs and indications that we are overestimating distances to giants, especially in young clusters.
The Astrophysical Journal, 2013
In the standard model of cosmology, structure emerges out of a non-rotational flow and the angula... more In the standard model of cosmology, structure emerges out of a non-rotational flow and the angular momentum of collapsing halos is induced by tidal torques. The growth of angular momentum in the linear and quasi-linear phases is associated with a shear, curl-free, flow and it is well described within the linear framework of tidal torque theory (TTT). However, TTT ceases to be applicable as halos approach turnaround when their ambient flow field becomes rotational. Subsequently, halos become embedded in a vortical flow field and the growth of their angular momentum is affected by the vorticity of their ambient velocity field. Using a cosmological simulation, we have examined the importance of the curl of the velocity field in determining halo spin, finding a significant alignment between the two: the vorticity tends to be perpendicular to the axis of the fastest collapse of the velocity shear tensor (e 1). This is independent of halo masses and cosmic web environment. Our results agree with previous findings on the tendency of halo spin to be perpendicular to e 1 , and of the spin of (simulated) halos and (observed) galaxies to be aligned with the large-scale structure. It follows that angular momentum growth proceeds in two distinct phases. First, the angular momentum emerges out of a shear, curl-free, potential flow, as described by TTT. In the second phase, in which halos approach virialization, the angular momentum emerges out of a vortical flow and halo spin becomes partially aligned with the vorticity of the ambient flow field.
The Astrophysical Journal Supplement Series, 2012
The RAdial Velocity Experiment (RAVE) is a medium-resolution (R ∼ 7500) spectroscopic survey of t... more The RAdial Velocity Experiment (RAVE) is a medium-resolution (R ∼ 7500) spectroscopic survey of the Milky Way that has already obtained over half a million stellar spectra. They present a randomly selected magnitude-limited sample, so it is important to use a reliable and automated classification scheme that identifies normal single stars and discovers different types of peculiar stars. To this end, we present a morphological classification of ∼350,000 RAVE survey stellar spectra using locally linear embedding, a dimensionality reduction method that enables representing the complex spectral morphology in a low-dimensional projected space while still preserving the properties of the local neighborhoods of spectra. We find that the majority of all spectra in the database (∼90%-95%) belong to normal single stars, but there is also a significant population of several types of peculiars. Among them, the most populated groups are those of various types of spectroscopic binary and chromospherically active stars. Both of them include several thousands of spectra. Particularly the latter group offers significant further investigation opportunities since activity of stars is a known proxy of stellar ages. Applying the same classification procedure to the sample of normal single stars alone shows that the shape of the projected manifold in two-dimensional space correlates with stellar temperature, surface gravity, and metallicity.
The Astrophysical Journal Supplement Series, 2006
This paper describes the fourth data release of the Sloan Digital Sky Survey (SDSS), including al... more This paper describes the fourth data release of the Sloan Digital Sky Survey (SDSS), including all survey-quality data taken through June 2004. The data release includes five-band photometric data for 180 million objects selected over 6670 deg 2 , and 673,280 spectra of galaxies, quasars, and stars selected from 4783 deg 2 of that imaging data using the standard SDSS target selection algorithms. These numbers represent a roughly 25% increment over those of the Third Data Release. The Fourth Data Release also includes an additional 131,840 spectra of objects selected using a variety of alternative algorithms, to address scientific issues ranging from the kinematics of stars in the Milky Way thick disk to populations of faint galaxies and quasars.
The Astrophysical Journal Supplement Series, 2009
This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the... more This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11,663 deg 2 of imaging data, with most of the ∼2000 deg 2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry on a 120 • long, 2. • 5 wide stripe along the celestial equator in the Southern Galactic Cap, with some regions covered by as many as 90 individual imaging runs. We include a co-addition of the best of these data, going roughly 2 mag fainter than the main survey over 250 deg 2. The survey has completed spectroscopy over 9380 deg 2 ; the spectroscopy is now complete over a large contiguous area of the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog, reducing the rms statistical errors at the bright end to 45 milliarcseconds per coordinate. We further quantify a systematic error in bright galaxy photometry due to poor sky determination; this problem is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.
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Papers by Matthias Steinmetz