Flux- and volume-limited groups/clusters for the SDSS galaxies: catalogues and mass estimation

We provide flux-limited and volume-limited galaxy group and cluster catalogues, based on the spectroscopic sample of the SDSS data release 10 galaxies. We used a modified friends-of-friends (FoF) method with a variable linking length in the transverse and radial directions to identify as many realistic groups as possible. The flux-limited catalogue incorporates galaxies down to m_r = 17.77 mag. It includes 588193 galaxies and 82458 groups. The volume-limited catalogues are complete for absolute magnitudes down to M_r = -18.0, -18.5, -19.0, -19.5, -20.0, -20.5, and -21.0; the completeness is achieved within different spatial volumes, respectively. Our analysis shows that flux-limited and volume-limited group samples are well compatible to each other, especially for the larger groups/clusters. Dynamical mass estimates, based on radial velocity dispersions and group extent in the sky, are added to the extracted groups. The catalogues can be accessed via http://cosmodb.to.ee and the Strasbourg Astronomical Data Center (CDS).Comment: 16 pages, 18 figures, 2 tables, accepted for publication in A&

The rapid evolution of the born-again giant Sakurai’s object

The extraordinarily rapid evolution of the born-again giant Sakurai’s object following discovery in 1996 has been investigated. The evolution can be traced both in a continued cooling of the stellar surface and dramatic changes in chemical composition on a timescale of a mere few months. The abundance alterations are the results of the mixing and nuclear reactions which have ensued due to the final He-shell flash which occurred during the descent along the white dwarf cooling track. The observed changes in the H and Li abundances can be explained by ingestion and burning of the H-rich envelope and Li-production through the Cameron-Fowler mechanism. The rapidly increasing abundances of the light s-elements (including Sc) are consistent with current s-processing by neutrons released from the concomitantly produced 13C. However, the possibility that the s-elements have previously been synthesized during the AGB-phase and only mixed to the surface in connection with the final He-shell flash in the pre-white dwarf cannot be convincingly ruled out either. Since Sakurai’s object shows substantial abundance similarities with the R CrB stars and has recently undergone R CrB-like visual fading events, the “birth” of an R CrB star may have been witnessed for the first time ever. Sakurai’s object thus lends strong support for the suggestion that at least some of the R CrB stars have been formed through a final He-shell flash in a post-AGB star

Recovering 3D structural properties of galaxies from SDSS-like photometry

Because of the 3D nature of galaxies, an algorithm for constructing spatial density distribution models of galaxies on the basis of galaxy images has many advantages over surface density distribution approximations. We present a method for deriving spatial structure and overall parameters of galaxies from images and estimate its accuracy and derived parameter degeneracies on a sample of idealised model galaxies. The test galaxies consist of a disc-like component and a spheroidal component with varying proportions and properties. Both components are assumed to be axially symmetric and coplanar. We simulate these test galaxies as if observed in the SDSS project through ugriz filters, thus gaining a set of realistically imperfect images of galaxies with known intrinsic properties. These artificial SDSS galaxies were thereafter remodelled by approximating the surface brightness distribution with a 2D projection of a bulge+disc spatial distribution model and the restored parameters were compared to the initial ones. Down to the r-band limiting magnitude 18, errors of the restored integral luminosities and colour indices remain within 0.05 mag and errors of the luminosities of individual components within 0.2 mag. Accuracy of the restored bulge-to-disc ratios (B/D) is within 40% in most cases, and becomes worse for galaxies with low B/D, but the general balance between bulges and discs is not shifted systematically. Assuming that the intrinsic disc axial ratio is < 0.3, the inclination angles can be estimated with errors < 5deg for most of the galaxies with B/D < 2 and with errors < 15deg up to B/D = 6. Errors of the recovered sizes of the galactic components are below 10% in most cases. In general, models of disc components are more accurate than models of spheroidal components for geometrical reasons.Comment: 15 pages, 13 figures, accepted for publication in RA

Near-Infrared Spectroscopy of Carbon-Enhanced Metal-Poor Stars. I. A SOAR/OSIRIS Pilot Study

We report on an abundance analysis for a pilot study of seven Carbon-Enhanced Metal-Poor (CEMP) stars, based on medium-resolution optical and near-infrared spectroscopy. The optical spectra are used to estimate [Fe/H], [C/Fe], [N/Fe], and [Ba/Fe] for our program stars. The near-infrared spectra, obtained during a limited early science run with the new SOAR 4.1m telescope and the Ohio State Infrared Imager and Spectrograph (OSIRIS), are used to obtain estimates of [O/Fe] and 12C/13C. The chemical abundances of CEMP stars are of importance for understanding the origin of CNO in the early Galaxy, as well as for placing constraints on the operation of the astrophysical s-process in very low-metallicity Asymptotic Giant Branch (AGB) stars. This pilot study includes a few stars with previously measured [Fe/H], [C/Fe], [N/Fe],[O/Fe], 12C/13C, and [Ba/Fe], based on high-resolution optical spectra obtained with large-aperture telescopes. Our analysis demonstrates that we are able to achieve reasonably accurate determinations of these quantities for CEMP stars from moderate-resolution optical and near-infrared spectra. This opens the pathway for the study of significantly larger samples of CEMP stars in the near future. Furthermore, the ability to measure [Ba/Fe] for (at least the cooler) CEMP stars should enable one to separate stars that are likely to be associated with s-process enhancements (the CEMP-s stars) from those that do not exhibit neutron-capture enhancements (the CEMP-no stars).Comment: 27 pages, including 5 tables, 6 figures, accepted for publication in The Astronomical Journa

Variability in content and dissolution profiles of MDMA tablets collected in the UK between 2001 and 2018-A potential risk to users?

Official Student Newspaper Issue is 12 pages long

Sakurai's Object: characterizing the near-infrared CO ejecta between 2003 and 2007

We present observations of Sakurai's Object obtained at 1–5 μm between 2003 and 2007. By fitting a radiative transfer model to an echelle spectrum of CO fundamental absorption features around 4.7 μm, we determine the excitation conditions in the line-forming region. We find 12C/13C = 3.5+2.0−1.5, consistent with CO originating in ejecta processed by the very late thermal pulse, rather than in the pre-existing planetary nebula. We demonstrate the existence of 2.2 × 10−6≤MCO≤ 2.7 × 10−6 M⊙ of CO ejecta outside the dust, forming a high-velocity wind of 500 ± 80 km s−1. We find evidence for significant weakening of the CO band and cooling of the dust around the central star between 2003 and 2005. The gas and dust temperatures are implausibly high for stellar radiation to be the sole contributor

Simultaneous Determination of Fluoroquinolones and Sulfonamides Originating from Sewage Sludge Compost

A simultaneous method for quantitative determination of traces of fluoroquinolones (FQs) and sulfonamides (SAs) in edible plants fertilized with sewage sludge was developed. The compounds were extracted from the plants by rapid and simple liquid extraction followed by extracts clean-up using solid phase extraction. The eluent additive 1,1,1,3,3,3-hexafluoro-2-propanol was used for liquid chromatographic detection to achieve separation of structurally similar antimicrobials like ciprofloxacin and norfloxacin. Identification and quantification of the compounds were performed using high-performance liquid chromatography with electrospray ionization mass spectrometry in selected reaction monitoring mode. Method was validated and extraction recoveries of FQs and SAs ranged from 66% to 93%. The limit of quantifications was from 5 ng/g in the case of ofloxacin to 40 ng/g for norfloxacin. The method precision ranged from 1.43% to 2.61%. The developed novel method was used to evaluate the plats antimicrobial uptake (potato (Solanum tuberosum L.), carrot (Daucus carota L.), lettuce (Lactuca sativa L.), and wheat (Triticum vulgare L.)) from soil and migration of the analytes inside the plants