M. Krupa

SALT long-slit spectroscopy of LBQS 2113-4538: variability of the Mg II and Fe II component

Context. The Mg II line is of extreme importance in intermediate redshift quasars since it allows us to measure the black hole mass in these sources and to use these sources as probes of the distribution of dark energy in the Universe, as a complementary tool to SN Ia. Aims. Reliable use of Mg II requires a good understanding of all the systematic effects involved in the measurement of the line properties, including the contamination by Fe II UV emission. Methods. We performed three spectroscopic observations of a quasar LBQS 2113-4538 (z = 0.956) with the SALT telescope, separated in time by several months and we analyze in detail the mean spectrum and the variability in the spectral shape. Results. We show that even in our good-quality spectra the Mg II doublet is well fit by a single Lorentzian shape. We tested several models of the Fe II pseudo-continuum and showed that one of them well represents all the data. The amplitudes of both components vary in time, but the shapes do not change significantly. The measured line width of LBQS 2113-4538 identifies this object as a class A quasar. The upper limit of 3% for the contribution of the narrow line region (NLR) to Mg II may suggest that the separation of the broad line region and NLR disappears in this class of objects.

SALT long-slit spectroscopy of CTS C30.10: two-component Mg II line

Context. Quasars can be used as a complementary tool to SN Ia to probe the distribution of dark energy in the Universe by measuring the time delay of the emission line with respect to the continuum. The understanding of the Mg II emission line structure is important for cosmological application and for the black hole mass measurements of intermediate redshift quasars. Aims. Knowing the shape of Mg II line and its variability allows for identifying which part of the line should be used to measure the time delay and the black hole mass. We thus aim at determining the structure and the variability of the Mg II line, as well as the underlying Fe II pseudo-continuum. Methods. We performed five spectroscopic observations of a quasar CTS C30.10 (z = 0.9000) with the SALT telescope between December 2012 and March 2014, and we studied the variations in the spectral shape in the 2700 A−2900 A rest frame. Results. We show that the Mg II line in this source consists of two kinematic components, which makes the source representative of type B quasars. Both components were modeled well with a Lorentzian shape, and they vary in a similar way. The Fe II contribution seems to be related only to the first (blue) Mg II component. Broad band spectral fitting instead favor the use of the whole line profile. The contribution of the narrow line region to Mg II is very low, below 2%. The Mg II variability is lower than the variability of the continuum, which is consistent with the simple reprocessing scenario. The variability level of CTS C30.10 and the measurement accuracy of the line and continuum is high enough to expect that further monitoring will allow the time delay between the Mg II line and continuum to be measured.

Machine-learning identification of galaxies in the WISE × SuperCOSMOS all-sky catalogue

Context. The two currently largest all-sky photometric datasets, WISE and SuperCOSMOS, have been recently cross-matched to construct a novel photometric redshift catalogue on 70% of the sky. Galaxies were separated from stars and quasars through colour cuts, which may leave imperfections because different source types may overlap in colour space. Aims. The aim of the present work is to identify galaxies in the WISE × SuperCOSMOS catalogue through an alternative approach of machine learning. This allows us to define more complex separations in the multi-colour space than is possible with simple colour cuts, and should provide a more reliable source classification. Methods. For the automatised classification we used the support vector machines (SVM) learning algorithm and employed SDSS spectroscopic sources that we cross-matched with WISE × SuperCOSMOS to construct the training and verification set. We performed a number of tests to examine the behaviour of the classifier (completeness, purity, and accuracy) as a function of source apparent magnitude and Galactic latitude. We then applied the classifier to the full-sky data and analysed the resulting catalogue of candidate galaxies. We also compared the resulting dataset with the one obtained through colour cuts. Results. The tests indicate very high accuracy, completeness, and purity (>95%) of the classifier at the bright end; this deteriorates for the faintest sources, but still retains acceptable levels of ~85%. No significant variation in the classification quality with Galactic latitude is observed. When we applied the classifier to all-sky WISE × SuperCOSMOS data, we found 15 million galaxies after masking problematic areas. The resulting sample is purer than the one produced by applying colour cuts, at the price of a lower completeness across the sky. Conclusions. The automatic classification is a successful alternative approach to colour cuts for defining a reliable galaxy sample. The identifications we obtained are included in the public release of the WISE × SuperCOSMOS galaxy catalogue.

The mass of the black hole in RE J1034+396

Context. The black hole mass measurement in active galaxies is a challenge, particularly in sources where the reverberation method cannot be applied. Aims. We aim to determine the black hole mass in a very special object, RE J1034+396, one of the two active galactic nuclei (AGN) with quasi-periodic oscillations detected in X-rays, and a single bright AGN with optical band totally dominated by starlight. Methods. We fit the stellar content using the code starlight, and the broad band disk contribution to optical/UV/X-ray emission is modeled with OPTXAGNF. Based on starlight, we develop our own code OPTGAL for simultaneous fitting of the stellar, Fe II, and BC content in the optical/UV/X-ray data. We also determine the black hole mass using several other independent methods. Results. Various methods give contradictory results. Most measurements of the black hole mass are in the range 10 6 −10 7 M ⊙ , and the measurements based on dynamics give higher values than measurements based on H β and Mg II emission lines.

SALT long-slit spectroscopy of quasar HE 0435-4312: fast displacement of the Mg II emission line

Context. The Mg II emission line is visible in the optical band for intermediate redshift quasars (0.4 We aim to determine the substructure and the variability of the Mg II line with the aim to identify which part of the line comes from a medium in Keplerian motion.Methods. Using the Southern African Large Telescope (SALT) with the Robert Stobie Spectrograph (RSS) we performed ten spectroscopic observations of quasar HE 0435-4312 (z = 1.2231) over a period of three years (Dec. 23/24, 2012 to Dec. 7/8, 2015).Results. Both the Mg II line and the Fe II pseudo-continuum increase with time. We clearly detect the systematic shift of the Mg II line with respect to the Fe II over the years, corresponding to the acceleration of 104 ± 14 km s-1 yr-1 in the quasar rest frame. The Mg II line shape is clearly non-Gaussian but single-component, and the increase in line equivalent width and line shift is not accompanied with significant evolution of the line shape. We analyse the conditions in the Mg II and Fe II formation region and we note that the very large difference in the covering factor and the turbulent velocity also support the conclusion that the two regions are spatially separated.Conclusions. The measured acceleration of the line systematic shift is too large to connect it with the orbital motion at a distance of the BLR in this source. It may imply a precessing inner disk illuminating the BLR. Further monitoring is still needed to better constrain the variability mechanism.

Quasars as tracers of cosmic flows

Quasars, as the most luminous persistent sources in the Universe, have broad applications for cosmological studies. In particular, they can be employed to directly measure the expansion history of the Universe, similarly to SNe Ia. The advantage of quasars is that they are numerous, cover a broad range of redshifts, up to

Towards automatic classification of all WISE sources

z = 7

The dust origin of the Broad Line Region and the model consequences for AGN unification scheme

, and do not show significant evolution of metallicity with redshift. The idea is based on the relation between the time delay of an emission line and the continuum, and the absolute monochromatic luminosity of a quasar. For intermediate redshift quasars, the suitable line is Mg II. Between December 2012 and March 2014, we performed five spectroscopic observations of the QSO CTS C30.10 (

SALT long-slit spectroscopy of HE 0435-4312: fast change in the Mg II emission line shape

z = 0.900

Tracing dark energy with quasars

) using the South African Large Telesope (SALT), supplemented with photometric monitoring, with the aim of determining the variability of the line shape, changes in the total line intensity and in the continuum. We show that the method is very promising.