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- ItemGaia Data Release 2 : Properties and validation of the radial velocities(Les Ulis : EDP Sciences, 2019) Katz, D.; Sartoretti, P.; Cropper, M.; Panuzzo, P.; Seabroke, G.M.; Viala, Y.; Benson, K.; Blomme, R.; Jasniewicz, G.; Jean-Antoine, A.; Huckle, H.; Smith, M.; Baker, S.; Crifo, F.; Damerdji, Y.; David, M.; Dolding, C.; Frémat, Y.; Gosset, E.; Guerrier, A.; Guy, L. P.; Haigron, R.; Janßen, K.; Marchal, O.; Plum, G.; Soubiran, C.; Thévenin, F.; Ajaj, M.; Allende Prieto, C.; Babusiaux, C.; Boudreault, S.; Chemin, L.; Delle Luche, C.; Fabre, C.; Gueguen, A.; Hambly, N. C.; Lasne, Y.; Meynadier, F.; Pailler, F.; Panem, C.; Royer, F.; Tauran, G.; Zurbach, C.; Zwitter, T.; Arenou, F.; Bossini, D.; Gerssen, J.; Gómez, A.; Lemaitre, V.; Leclerc, N.; Morel, T.; Munari, U.; Turon, C.; Vallenari, A.; Žerjal, M.Context. For Gaia DR2, 280 million spectra collected by the Radial Velocity Spectrometer instrument on board Gaia were processed, and median radial velocities were derived for 9.8 million sources brighter than GRVS = 12 mag. Aims. This paper describes the validation and properties of the median radial velocities published in Gaia DR2. Methods. Quality tests and filters were applied to select those of the 9.8 million radial velocities that have the quality to be published in Gaia DR2. The accuracy of the selected sample was assessed with respect to ground-based catalogues. Its precision was estimated using both ground-based catalogues and the distribution of the Gaia radial velocity uncertainties. Results. Gaia DR2 contains median radial velocities for 7 224 631 stars, with Teff in the range [3550; 6900] K, which successfully passed the quality tests. The published median radial velocities provide a full-sky coverage and are complete with respect to the astrometric data to within 77.2% (for G ≤ 12:5 mag). The median radial velocity residuals with respect to the ground-based surveys vary from one catalogue to another, but do not exceed a few 100 m s-1. In addition, the Gaia radial velocities show a positive trend as a function of magnitude, which starts around GRVS ∼ 9 mag and reaches about +500 m s-1 at GRVS = 11:75 mag. The origin of the trend is under investigation, with the aim to correct for it in Gaia DR3. The overall precision, estimated from the median of the Gaia radial velocity uncertainties, is 1.05 km s-1. The radial velocity precision is a function of many parameters, in particular, the magnitude and effective temperature. For bright stars, GRVS 2 [4; 8] mag, the precision, estimated using the full dataset, is in the range 220-350 m s-1, which is about three to five times more precise than the pre-launch specification of 1 km s-1. At the faint end, GRVS = 11:75 mag, the precisions for Teff = 5000 and 6500 K are 1.4 and 3.7 km s-1, respectively.
- ItemThe eROSITA X-ray telescope on SRG(Les Ulis : EDP Sciences, 2021) Predehl, P.; Andritschke, R.; Arefiev, V.; Babyshkin, V.; Batanov, O.; Becker, W.; Böhringer, H.; Bogomolov, A.; Boller, T.; Borm, K.; Bornemann, W.; Bräuninger, H.; Brüggen, M.; Brunner, H.; Brusa, M.; Bulbul, E.; Buntov, M.; Burwitz, V.; Burkert, W.; Clerc, N.; Churazov, E.; Coutinho, D.; Dauser, T.; Dennerl, K.; Doroshenko, V.; Eder, J.; Emberger, V.; Eraerds, T.; Finoguenov, A.; Freyberg, M.; Friedrich, P.; Friedrich, S.; Fürmetz, M.; Georgakakis, A.; Gilfanov, M.; Granato, S.; Grossberger, C.; Gueguen, A.; Gureev, P.; Haberl, F.; Hälker, O.; Hartner, G.; Hasinger, G.; Huber, H.; Ji, L.; Kienlin, A. v.; Kink, W.; Korotkov, F.; Kreykenbohm, I.; Lamer, G.; Lomakin, I.; Lapshov, I.; Liu, T.; Maitra, C.; Meidinger, N.; Menz, B.; Merloni, A.; Mernik, T.; Mican, B.; Mohr, J.; Müller, S.; Nandra, K.; Nazarov, V.; Pacaud, F.; Pavlinsky, M.; Perinati, E.; Pfeffermann, E.; Pietschner, D.; Ramos-Ceja, M. E.; Rau, A.; Reiffers, J.; Reiprich, T. H.; Robrade, J.; Salvato, M.; Sanders, J.; Santangelo, A.; Sasaki, M.; Scheuerle, H.; Schmid, C.; Schmitt, J.; Schwope, A.; Shirshakov, A.; Steinmetz, M.; Stewart, I.; Strüder, L.; Sunyaev, R.; Tenzer, C.; Tiedemann, L.; Trümper, J.; Voron, V.; Weber, P.; Wilms, J.; Yaroshenko, V.eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the primary instrument on the Spectrum-Roentgen-Gamma (SRG) mission, which was successfully launched on July 13, 2019, from the Baikonour cosmodrome. After the commissioning of the instrument and a subsequent calibration and performance verification phase, eROSITA started a survey of the entire sky on December 13, 2019. By the end of 2023, eight complete scans of the celestial sphere will have been performed, each lasting six months. At the end of this program, the eROSITA all-sky survey in the soft X-ray band (0.2-2.3 keV) will be about 25 times more sensitive than the ROSAT All-Sky Survey, while in the hard band (2.3-8 keV) it will provide the first ever true imaging survey of the sky. The eROSITA design driving science is the detection of large samples of galaxy clusters up to redshifts z > 1 in order to study the large-scale structure of the universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of a few million AGNs, including obscured objects, revolutionizing our view of the evolution of supermassive black holes. The survey will also provide new insights into a wide range of astrophysical phenomena, including X-ray binaries, active stars, and diffuse emission within the Galaxy. Results from early observations, some of which are presented here, confirm that the performance of the instrument is able to fulfil its scientific promise. With this paper, we aim to give a concise description of the instrument, its performance as measured on ground, its operation in space, and also the first results from in-orbit measurements.
- ItemGaia Early Data Release 3: Gaia photometric science alerts(Les Ulis : EDP Sciences, 2021) Hodgkin, S.T.; Harrison, D.L.; Breedt, E.; Wevers, T.; Rixon, G.; Delgado, A.; Yoldas, A.; Kostrzewa-Rutkowska, Z.; Wyrzykowski, Ł.; van Leeuwen, M.; Blagorodnova, N.; Serraller, I.; Steeghs, D.; Sullivan, M.; Szabados, L.; Szegedi-Elek, E.; Tisserand, P.; Tomasella, L.; van Velzen, S.; Whitelock, P.A; Wilson, R.W.; Campbell, H.; Young, D.R.; Eappachen, D.; Fraser, M.; Ihanec, N.; Koposov, S.E.; Kruszyńska, K.; Marton, G.; Rybicki, K.A.; Brown, A.G.A.; Burgess, P. W.; Busso, G.; Cowell, S.; De Angeli, F.; Diener, C.; Evans, D.W.; Gilmore, G.; Holland, G.; Jonker, P.G.; van Leeuwen, F.; Mignard, F.; Osborne, P.J.; Portell, J.; Prusti, T.; Richards, P.J.; Riello, M.; Seabroke, G.M.; Walton, N.A.; Ábrahám, Péter; Altavilla, G.; Baker, S.G.; Bastian, U.; O'Brien, P.; de Bruijne, J.; Butterley, T.; Carrasco, J.M.; Castañeda, J.; Clark, J.S.; Clementini, G.; Copperwheat, C.M.; Cropper, M.; Damljanovic, G.; Davidson, M.; Davis, C.J.; Dennefeld, M.; Dhillon, V.S.; Dolding, C.; Dominik, M.; Esquej, P.; Eyer, L.; Fabricius, C.; Fridman, M.; Froebrich, D.; Garralda, N.; Gomboc, A.; González-Vidal, J.J.; Guerra, R.; Hambly, N.C.; Hardy, L.K.; Holl, B.; Hourihane, A.; Japelj, J.; Kann, D.A.; Kiss, C.; Knigge, C.; Kolb, U.; Komossa, S.; Kóspál, Á.; Kovács, G.; Kun, M.; Leto, G.; Lewis, F.; Littlefair, S.P.; Mahabal, A.A.; Mundell, C.G.; Nagy, Z.; Padeletti, D.; Palaversa, L.; Pigulski, A.; Pretorius, M.L.; van Reeven, W.; Ribeiro, V.A.R.M.; Roelens, M.; Rowell, N.; Schartel, N.; Scholz, A.; Schwope, A.; Sipőcz, B.M.; Smartt, S.J.; Smith, M.D.Context. Since July 2014, the Gaia mission has been engaged in a high-spatial-resolution, time-resolved, precise, accurate astrometric, and photometric survey of the entire sky. Aims. We present the Gaia Science Alerts project, which has been in operation since 1 June 2016. We describe the system which has been developed to enable the discovery and publication of transient photometric events as seen by Gaia. Methods. We outline the data handling, timings, and performances, and we describe the transient detection algorithms and filtering procedures needed to manage the high false alarm rate. We identify two classes of events: (1) sources which are new to Gaia and (2) Gaia sources which have undergone a significant brightening or fading. Validation of the Gaia transit astrometry and photometry was performed, followed by testing of the source environment to minimise contamination from Solar System objects, bright stars, and fainter near-neighbours. Results. We show that the Gaia Science Alerts project suffers from very low contamination, that is there are very few false-positives. We find that the external completeness for supernovae, CE = 0.46, is dominated by the Gaia scanning law and the requirement of detections from both fields-of-view. Where we have two or more scans the internal completeness is CI = 0.79 at 3 arcsec or larger from the centres of galaxies, but it drops closer in, especially within 1 arcsec. Conclusions. The per-Transit photometry for Gaia transients is precise to 1% at G = 13, and 3% at G = 19. The per-Transit astrometry is accurate to 55 mas when compared to Gaia DR2. The Gaia Science Alerts project is one of the most homogeneous and productive transient surveys in operation, and it is the only survey which covers the whole sky at high spatial resolution (subarcsecond), including the Galactic plane and bulge. © S. T. Hodgkin et al. 2021.
- ItemThe Gaia -ESO Survey: Lithium measurements and new curves of growth(Les Ulis : EDP Sciences, 2022) Franciosini, E.; Randich, S.; de Laverny, P.; Biazzo, K.; Feuillet, D.K.; Frasca, A.; Lind, K.; Prisinzano, L.; Tautvaišiene, G.; Lanzafame, A.C.; Smiljanic, R.; Gonneau, A.; Magrini, L.; Pancino, E.; Guiglion, G.; Sacco, G.G.; Sanna, N.; Gilmore, G.; Bonifacio, P.; Jeffries, R.D.; Micela, G.; Prusti, T.; Alfaro, E.J.; Bensby, T.; Bragaglia, A.; François, P.; Korn, A.J.; Van Eck, S.; Bayo, A.; Bergemann, M.; Carraro, G.; Heiter, U.; Hourihane, A.; Jofré, P.; Lewis, J.; Martayan, C.; Monaco, L.; Morbidelli, L.; Worley, C.C.; Zaggia, S.Context. The Gaia-ESO Survey (GES) is a large public spectroscopic survey that was carried out using the multi-object FLAMES spectrograph at the Very Large Telescope. The survey provides accurate radial velocities, stellar parameters, and elemental abundances for ~115 000 stars in all Milky Way components. Aims. In this paper, we describe the method adopted in the final data release to derive lithium equivalent widths (EWs) and abundances. Methods. Lithium EWs were measured using two different approaches for FGK and M-type stars, to account for the intrinsic differences in the spectra. For FGK stars, we fitted the lithium line using Gaussian components, while direct integration over a predefined interval was adopted for M-type stars. Care was taken to ensure continuity between the two regimes. Abundances were derived using a new set of homogeneous curves of growth that were derived specifically for GES, and which were measured on a synthetic spectral grid consistently with the way the EWs were measured. The derived abundances were validated by comparison with those measured by other analysis groups using different methods. Results. Lithium EWs were measured for ~40 000 stars, and abundances could be derived for ~38 000 of them. The vast majority of the measures (80%) have been obtained for stars in open cluster fields. The remaining objects are stars in globular clusters, or field stars in the Milky Way disc, bulge, and halo. Conclusions. The GES dataset of homogeneous lithium abundances described here will be valuable for our understanding of several processes, from stellar evolution and internal mixing in stars at different evolutionary stages to Galactic evolution.
- ItemGaia Data Release 2 : Processing the spectroscopic data(Les Ulis : EDP Sciences, 2018) Sartoretti, P.; Katz, D.; Cropper, M.; Panuzzo, P.; Seabroke, G. M.; Viala, Y.; Benson, K.; Blomme, R.; Jasniewicz, G.; Jean-Antoine, A.; Huckle, H.; Smith, M.; Baker, S.; Crifo, F.; Damerdji, Y.; David, M.; Dolding, C.; Frémat, Y.; Gosset, E.; Guerrier, A.; Guy, L. P.; Haigron, R.; Janßen, K.; Marchal, O.; Plum, G.; Soubiran, C.; Thévenin, F.; Ajaj, M.; Allende Prieto, C.; Babusiaux, C.; Boudreault, S.; Chemin, L.; Delle Luche, C.; Fabre, C.; Gueguen, A.; Hambly, N. C.; Lasne, Y.; Meynadier, F.; Pailler, F.; Panem, C.; Riclet, F.; Royer, F.; Tauran, G.; Zurbach, C.; Zwitter, T.; Arenou, F.; Gomez, A.; Lemaitre, V.; Leclerc, N.; Morel, T.; Munari, U.; Turon, C.; Žerjal, M.Context. The Gaia Data Release 2 (DR2 ) contains the first release of radial velocities complementing the kinematic data of a sample of about 7 million relatively bright, late-type stars. Aims. This paper provides a detailed description of the Gaia spectroscopic data processing pipeline, and of the approach adopted to derive the radial velocities presented in DR2 . Methods. The pipeline must perform four main tasks: (i) clean and reduce the spectra observed with the Radial Velocity Spectrometer (RVS); (ii) calibrate the RVS instrument, including wavelength, straylight, line-spread function, bias non-uniformity, and photometric zeropoint; (iii) extract the radial velocities; and (iv) verify the accuracy and precision of the results. The radial velocity of a star is obtained through a fit of the RVS spectrum relative to an appropriate synthetic template spectrum. An additional task of the spectroscopic pipeline was to provide first-order estimates of the stellar atmospheric parameters required to select such template spectra. We describe the pipeline features and present the detailed calibration algorithms and software solutions we used to produce the radial velocities published in DR2 . Results. The spectroscopic processing pipeline produced median radial velocities for Gaia stars with narrow-band near-IR magnitude GRVS ≤ 12 (i.e. brighter than V ∼ 13). Stars identified as double-lined spectroscopic binaries were removed from the pipeline, while variable stars, single-lined, and non-detected double-lined spectroscopic binaries were treated as single stars. The scatter in radial velocity among different observations of a same star, also published in Gaia DR2, provides information about radial velocity variability. For the hottest (Te≥ 7000 K) and coolest (Te≤ 3500 K) stars, the accuracy and precision of the stellar parameter estimates are not sufficient to allow selection of appropriate templates. The radial velocities obtained for these stars were removed from DR2 . The pipeline also provides a first-order estimate of the performance obtained. The overall accuracy of radial velocity measurements is around ∼200-300 m s-1, and the overall precision is ∼1 km s-1; it reaches ∼200 m s-1 for the brightest stars.
- ItemSynthetic simulations of the extragalactic sky seen by eROSITA : I. Pre-launch selection functions from Monte-Carlo simulations(Les Ulis : EDP Sciences, 2018) Clerc, N.; Ramos-Ceja, M.E.; Ridl, J.; Lamer, G.; Brunner, H.; Hofmann, F.; Comparat, J.; Pacaud, F.; Käfer, F.; Reiprich, T.H.; Merloni, A.; Schmid, C.; Brand, T.; Wilms, J.; Friedrich, P.; Finoguenov, A.; Dauser, T.; Kreykenbohm, I.Context. Studies of galaxy clusters provide stringent constraints on models of structure formation. Provided that selection effects are under control, large X-ray surveys are well suited to derive cosmological parameters, in particular those governing the dark energy equation of state. Aims. We forecast the capabilities of the all-sky eROSITA (extended ROentgen Survey with an Imaging Telescope Array) survey to be achieved by the early 2020s. We bring special attention to modelling the entire chain from photon emission to source detection and cataloguing. Methods. The selection function of galaxy clusters for the upcoming eROSITA mission is investigated by means of extensive and dedicated Monte-Carlo simulations. Employing a combination of accurate instrument characterisation and a state-of-the-art source detection technique, we determine a cluster detection efficiency based on the cluster fluxes and sizes. Results. Using this eROSITA cluster selection function, we find that eROSITA will detect a total of approximately 105 clusters in the extra-galactic sky. This number of clusters will allow eROSITA to put stringent constraints on cosmological models. We show that incomplete assumptions on selection effects, such as neglecting the distribution of cluster sizes, induce a bias in the derived value of cosmological parameters. Conclusions. Synthetic simulations of the eROSITA sky capture the essential characteristics impacting the next-generation galaxy cluster surveys and they highlight parameters requiring tight monitoring in order to avoid biases in cosmological analyses.
- ItemA self-consistent dynamical model of the Milky Way disc adjusted to Gaia data(Les Ulis : EDP Sciences, 2022) Robin, A.C.; Bienaymé, O.; Salomon, J.B.; Reylé, C.; Lagarde, N.; Figueras, F.; Mor, R.; Fernández-Trincado, J.G.; Montillaud, J.Context. Accurate astrometry achieved by Gaia for many stars in the Milky Way provides an opportunity to reanalyse the Galactic stellar populations from a large and homogeneous sample and to revisit the Galaxy gravitational potential. Aims. This paper shows how a self-consistent dynamical model can be obtained by fitting the gravitational potential of the Milky Way to the stellar kinematics and densities from Gaia data. Methods. We derived a gravitational potential using the Besancon Galaxy Model, and computed the disc stellar distribution functions based on three integrals of motion (E, Lz, I3) to model stationary stellar discs. The gravitational potential and the stellar distribution functions are built self-consistently, and are then adjusted to be in agreement with the kinematics and the density distributions obtained from Gaia observations. A Markov chain Monte Carlo (MCMC) is used to fit the free parameters of the dynamical model to Gaia parallax and proper motion distributions. The fit is done on several sets of Gaia data, mainly a subsample of the GCNS (Gaia catalogue of nearby stars to 100 pc) with G< 17, together with 26 deep fields selected from eDR3, widely spread in longitudes and latitudes. Results. We are able to determine the velocity dispersion ellipsoid and its tilt for subcomponents of different ages, both varying with R and z. The density laws and their radial scale lengths for the thin and thick disc populations are also obtained self-consistently. This new model has some interesting characteristics that come naturally from the process, such as a flaring thin disc. The thick disc is found to present very distinctive characteristics from the old thin disc, both in density and kinematics. This lends significant support to the idea that thin and thick discs were formed in distinct scenarios, as the density and kinematics transition between them is found to be abrupt. The dark matter halo is shown to be nearly spherical. We also derive the solar motion with regards to the Local Standard of Rest (LSR), finding U· = 10.79 ± 0.56 km s-1, V· = 11.06 ± 0.94 km s-1, and W· = 7.66 ± 0.43 km s-1, in close agreement with recent studies. Conclusions. The resulting fully self-consistent gravitational potential, still axisymmetric, is a good approximation of a smooth mass distribution in the Milky Way and can be used for further studies, including finding streams, substructures, and to compute orbits for real stars in our Galaxy.
- ItemSustainable management of river oases along the Tarim River (SuMaRiO) in Northwest China under conditions of climate change(München : European Geopyhsical Union, 2015) Rumbaur, C.; Thevs, N.; Disse, M.; Ahlheim, M.; Brieden, A.; Cyffka, B.; Duethmann, D.; Feike, T.; Frör, O.; Gärtner, P.; Halik, Ü.; Hill, J.; Hinnenthal, M.; Keilholz, P.; Kleinschmit, B.; Krysanova, V.; Kuba, M.; Mader, S.; Menz, C.; Othmanli, H.; Pelz, S.; Schroeder, M.; Siew, T.F.; Stender, V.; Stahr, K.; Thomas, F.M.; Welp, M.; Wortmann, M.; Zhao, X.; Chen, X.; Jiang, T.; Luo, J.; Yimit, H.; Yu, R.; Zhang, X.; Zhao, C.The Tarim River basin, located in Xinjiang, NW China, is the largest endorheic river basin in China and one of the largest in all of Central Asia. Due to the extremely arid climate, with an annual precipitation of less than 100 mm, the water supply along the Aksu and Tarim rivers solely depends on river water. This is linked to anthropogenic activities (e.g., agriculture) and natural and semi-natural ecosystems as both compete for water. The ongoing increase in water consumption by agriculture and other human activities in this region has been enhancing the competition for water between human needs and nature. Against this background, 11 German and 6 Chinese universities and research institutes have formed the consortium SuMaRiO (Sustainable Management of River Oases along the Tarim River; http://www.sumario.de), which aims to create a holistic picture of the availability of water resources in the Tarim River basin and the impacts on anthropogenic activities and natural ecosystems caused by the water distribution within the Tarim River basin. On the basis of the results from field studies and modeling approaches as well as from suggestions by the relevant regional stakeholders, a decision support tool (DST) will be implemented that will then assist stakeholders in balancing the competition for water, acknowledging the major external effects of water allocation to agriculture and to natural ecosystems. This consortium was formed in 2011 and is funded by the German Federal Ministry of Education and Research. As the data collection phase was finished this year, the paper presented here brings together the results from the fields from the disciplines of climate modeling, cryology, hydrology, agricultural sciences, ecology, geoinformatics, and social sciences in order to present a comprehensive picture of the effects of different water availability schemes on anthropogenic activities and natural ecosystems along the Tarim River. The second objective is to present the project structure of the whole consortium, the current status of work (i.e., major new results and findings), explain the foundation of the decision support tool as a key product of this project, and conclude with application recommendations for the region. The discharge of the Aksu River, which is the major tributary of the Tarim, has been increasing over the past 6 decades. From 1989 to 2011, agricultural area more than doubled: cotton became the major crop and there was a shift from small-scale to large-scale intensive farming. The ongoing increase in irrigated agricultural land leads to the increased threat of salinization and soil degradation caused by increased evapotranspiration. Aside from agricultural land, the major natural and semi-natural ecosystems are riparian (Tugai) forests, shrub vegetation, reed beds, and other grassland, as well as urban and peri-urban vegetation. Within the SuMaRiO cluster, focus has been set on the Tugai forests, with Populus euphratica as the dominant tree species, because these forests belong to the most productive and species-rich natural ecosystems of the Tarim River basin. At sites close to the groundwater, the annual stem diameter increments of Populus euphratica correlated with the river runoffs of the previous year. However, the natural river dynamics cease along the downstream course and thus hamper the recruitment of Populus euphratica. A study on the willingness to pay for the conservation of the natural ecosystems was conducted to estimate the concern of the people in the region and in China's capital. These household surveys revealed that there is a considerable willingness to pay for conservation of the natural ecosystems, with mitigation of dust and sandstorms considered the most important ecosystem service. Stakeholder dialogues contributed to creating a scientific basis for a sustainable management in the future.
- ItemThe missing links of neutron star evolution in the eROSITA all-sky X-ray survey(Bristol : IOP Publ., 2017) Pires, A.M.The observational manifestation of a neutron star is strongly connected with the properties of its magnetic field. During the star's lifetime, the field strength and its changes dominate the thermo-rotational evolution and the source phenomenology across the electromagnetic spectrum. Signatures of magnetic field evolution are best traced among elusive groups of X-ray emitting isolated neutron stars (INSs), which are mostly quiet in the radio and γ-ray wavelengths. It is thus important to investigate and survey INSs in X-rays in the hope of discovering peculiar sources and the long-sought missing links that will help us to advance our understanding of neutron star evolution. The Extended Röntgen Survey with an Imaging Telescope Array (eROSITA), the primary instrument on the forthcoming Spectrum-RG mission, will scan the X-ray sky with unprecedented sensitivity and resolution. The survey has thus the unique potential to unveil the X-ray faint end of the neutron star population and probe sources that cannot be assessed by standard pulsar surveys.
- ItemReconciling radio relic observations and simulations: The NVSS sample(Trieste : SISSA, 2016) Gelszinnis, Jakob; Hoeft, Matthias; Nuza, Sebastián E.The diffusive shock acceleration scenario is usually invoked to explain radio relics, although the detailed driving mechanism is still a matter of debate. Our aim is to constrain models for the origin of radio relics by comparing observed relic samples with simulated ones. Here we present a framework to homogeneously extract the whole sample of known radio relics from NVSS so that it can be used for comparison with cosmological simulations. In this way, we can better handle intrinsic biases in the analysis of the radio relic population. In addition, we show some properties of the resulting NVSS sample relics such as the correlation between relic shape and orientation with respect to the cluster. Also, we briefly discuss the typical relic surface brightness and its relation to projected cluster distance and relic angular sizes.