arXiv subjects

H. Lietzen

Publications and source records attributed to H. Lietzen.

15 recordsLinked to original sources

arXiv2024

AXES-SDSS: comparison of SDSS galaxy groups with all-sky X-ray extended sources

We revisit the picture of X-ray emission of groups through the study of systematic differences in the optical properties of groups with and without X-ray emission and study the effect of large-scale density field on scaling relations. We present the identification of X-ray galaxy groups using a combination of RASS and SDSS data. We include new X-ray reanalysis of RASS, to include very extended (up to a size of half a degree) sources and account for differences in the limiting sensitivity towards compact and very extended X-ray emission. X-ray groups exhibit less scatter in the scaling relations and selecting the groups based on the extended X-ray emission leads to an additional scatter reduction. Most of the scatter for the optical groups is associated with a small (6%) fraction of outliers, primarily associated with low optical luminosity groups found in dense regions of the cosmic web. These groups are the primary candidates for being the contaminants in the optical group catalogues. Removing those groups from the optical group sample using optically measured properties only, leads to a substantial reduction in the scatter in the most scaling relations of the optical groups. We find a density dependence of both the X-ray and optical luminosity of groups, which we associate with the assembly bias. Abridged.

astro-ph.GA↗

arXiv2021

Velocity dispersion and dynamical mass for 270 galaxy clusters in the Planck PSZ1 catalogue

We present the velocity dispersion and dynamical mass estimates for 270 galaxy clusters included in the first Planck Sunyaev-Zeldovich (SZ) source catalogue, the PSZ1. Part of the results presented here were achieved during a two-year observational program, the ITP, developed at the Roque de los Muchachos Observatory (La Palma, Spain). In the ITP we carried out a systematic optical follow-up campaign of all the 212 unidentified PSZ1 sources in the northern sky that have a declination above $-15^\circ$ and are without known counterparts at the time of the publication of the catalogue. We present for the first time the velocity dispersion and dynamical mass of 58 of these ITP PSZ1 clusters, plus 35 newly discovered clusters that are not associated with the PSZ1 catalogue. Using Sloan Digital Sky Survey (SDSS) archival data, we extend this sample, including 212 already confirmed PSZ1 clusters in the northern sky. Using a subset of 207 of these galaxy clusters, we constrained the $M_{\rm SZ}$--$M_{\rm dyn}$ scaling relation, finding a mass bias of $(1-B) = 0.83\pm0.07$(stat)$\pm0.02$(sys). We show that this value is consistent with other results in the literature that were obtained with different methods (X-ray, dynamical masses, or weak-lensing mass proxies). This result cannot dissolve the tension between primordial cosmic microwave background anisotropies and cluster number counts in the $Ω_{\rm M}$--$σ_8$ plane.

astro-ph.CO↗

arXiv2020

Optical validation and characterisation of Planck PSZ1 sources at the Canary Islands observatories. II. Second year of ITP13 observations

We report new galaxy clusters previously unknown included in the PSZ1 catalogue. The results here presented have been achieved during the second year of a 2-year observational programme, the ITP13, developed at the Roque de los Muchachos Observatory (La Palma, Spain). We characterise 75 SZ sources with low SZ significance, SZ S/N$<5.32$ by performing deep optical imaging and spectroscopy in order to associate actual galaxy clusters to the SZ Planck source. We adopt robust criteria, based on the 2D-spatial distribution, richness and velocity dispersions to confirm actual optical counterparts up to $z<0.85$. At the end of the ITP13 observational programme, we study 256 SZ sources with $Dec \geq -15^{\circ}$ (212 of them completely unknown), finding optical counterparts for 152 SZ sources. The ITP13 validation programme has allowed us to update the PSZ1 purity, which is now more refined, increasing from 72\% to 83\% in the low SZ S/N regime. Our results are consistent with the predicted purity curve for the full PSZ1 catalogue and with the expected fraction of false detections caused by the non-Gaussian noise of foreground signals. Indeed, we find a strong correlation between the number of unconfirmed sources and the thermal emission of diffuse galactic dust at 857 GHz, thus increasing the fraction of false Planck SZ detections at low galactic latitudes.

astro-ph.CO↗

arXiv2019

Optical validation and characterization of Planck PSZ2 sources at the Canary Islands observatories. II. Second year of LP15 observations

We present the second and last year of observations of our optical follow-up programme 128-MULTIPLE-16/15B (LP15 )at Roque de los Muchachos Observatory (La Palma), which has been developed with the aim of validating all the unidentified PSZ2 sources in the northern sky, with declination above -15deg, and with no correspondence in the first Planck catalogue PSZ1. We adopt a robust confirmation criteria based on velocity dispersion and richness estimations in order to carry out the final classification of the new galaxy clusters as the optical counterparts of the PSZ2 detections. We also present final results of the programme, showing an update of the purity and completeness of the PSZ2 sample. After the LP15 programme, we find that the purity of the PSZ2 has increased from 76.7% originally to 86.2%. In addition, we study the possible reasons of having false detection, and we report a clear correlation between the number of unconfirmed sources and galactic thermal dust emission.

astro-ph.GA↗

arXiv2019

Optical validation and characterization of \Planck\ PSZ2 sources at the Canary Islands observatories. I. First year of LP15 observations

Using telescopes at the Canary Island observatories, we conducted the long-term observational programme 128-MULTIPLE-16/15B (LP15), a large and complete optical follow-up campaign of all the unidentified PSZ2 sources in the northern sky (Dec>-15 deg) and no correspondence in the first Planck catalogue PSZ1. We perform this optical validation of SZ clusters in order to contribute to the characterization of the actual purity and completeness of full Our validation procedure combines this optical information with SZ emission as traced by the publicly available Planck Compton y-maps. The clusters counterparts are classified according to redshift, velocity dispersion and richness of the clusters. This paper presents the detailed study of 106 objects out of the LP15 sample, corresponding to all the observations carried out during the first year of the programme. We confirmed the optical counterpart for 41 new PSZ2 sources, being 31 of them validated using also velocity dispersion based on our spectroscopic information. This is the largest dataset of newly confirmed PSZ2 sources without any previous optical information. All the confirmed counterparts are rich structures (i.e. they show high velocity dispersion), and are well aligned with the nominal Planck coordinates (~70% of them are located at less than 3 arcmin distance). In total, 65 SZ sources are classified as unconfirmed, being 57 of them due to the absence of an optical over-density, and 8 of them due to a weak association with the observed SZ decrement. Most of the sources with no optical counterpart are located at low galactic latitudes and present strong galactic cirrus in the optical images, being the dust contamination the most probable explanation for their inclusion in the PSZ2 catalogue.

astro-ph.CO↗

arXiv2018

Characterization of a subsample of the Planck SZ source cluster catalogues using optical SDSS DR12 data

The Planck catalogues of SZ sources, PSZ1 and PSZ2, are the largest catalogues of galaxy clusters selected through their SZ signature in the full sky. In 2013, we started a long-term observational program at Canary Island observatories with the aim of validating about 500 unconfirmed SZ sources. In this work we present results of the initial pre-screening of possible cluster counterparts using photometric and spectroscopic data of the Sloan Digital Sky Survey DR12. Our main aim is to identify previously unconfirmed PSZ2 cluster candidates and to contribute in determination of the actual purity and completeness of Planck SZ source sample. Using the latest version of the PSZ2 catalogue, we select all sources overlapping with the SDSS DR12 footprint and without redshift information. We validate these cluster fields following optical criteria (mainly distance with respect to the Planck pointing, magnitude of the brightest cluster galaxy and cluster richness) and combining them with the profiles of the Planck Compton y-maps. Together, this procedure allows for a more robust identification of optical counterparts compared to simply cross-matching with existing SDSS cluster catalogues that have been constructed from earlier SDSS Data Releases. The sample contains new redshifts for 37 Planck galaxy clusters that were not included in the original release of PSZ2 Planck catalogue. We detect three cases as possible multiple counterparts. We show that a combination of all available information (optical images and profile of SZ signal) can provide correct associations between the observed Planck SZ source and the optically identified cluster. We also show that Planck SZ detection is very sensitive even to high-z (z>0.5) clusters. In addition, we also present updated spectroscopic information for 34 Planck PSZ1 sources (33 previously photometrically confirmed and 1 new identification).

astro-ph.CO↗

arXiv2018

Optical validation and characterization of Planck PSZ1 sources at the Canary Islands observatories. I. First year of ITP13 observations

We identify new clusters and characterize previously unknown Planck Sunyaev-Zeldovich (SZ) sources from the first Planck catalogue of SZ sources (PSZ1). The results presented here correspond to an optical follow-up observational programme developed during approximately one year (2014) at Roque de los Muchachos Observatory, using the 2.5m Isaac Newton telescope, the 3.5m Telescopio Nazionale Galileo, the 4.2m William Herschel telescope and the 10.4m Gran Telescopio Canarias. We characterize 115 new PSZ1 sources using deep optical imaging and spectroscopy. We adopt robust criteria in order to consolidate the SZ counterparts by analysing the optical richness, the 2D galaxy distribution, and velocity dispersions of clusters. Confirmed counterparts are considered to be validated if they are rich structures, well aligned with the Planck PSZ1 coordinate and show relatively high velocity dispersion. Following this classification, we confirm 53 clusters, which means that 46% of this PSZ1 subsample has been validated and characterized with this technique. Sixty-two SZ sources (54% of this PSZ1 subset) remain unconfirmed. In addition, we find that the fraction of unconfirmed clusters close to the galactic plane (at |b|<25deg) is greater than that at higher galactic latitudes (|b|>25deg), which indicates contamination produced by radio emission of galactic dust and gas clouds on these SZ detections. In fact, in the majority of the cases, we detect important galactic cirrus in the optical images, mainly in the SZ target located at low galactic latitudes, which supports this hypothesis.

astro-ph.CO↗

arXiv2016

Supernova 2014J at M82: II. Direct Analysis of Spectra Obtained with Isaac Newton and William Herschel Telescopes

We analyze a time series of optical spectra of SN~2014J from almost two weeks prior to maximum to nearly four months after maximum. We perform our analysis using the SYNOW code, which is well suited to track the distribution of the ions with velocity in the ejecta. We show that almost all of the spectral features during the entire epoch can be identified with permitted transitions of the common ions found in normal SNe Ia in agreement with previous studies. We show that 2014J is a relatively normal SN Ia. At early times the spectral features are dominated by Si II, S II, Mg II, and Ca II. These ions persist to maximum light with the appearance of Na I and Mg I. At later times iron-group elements also appear, as expected in the stratified abundance model of the formation of normal type Ia SNe. We do not find significant spectroscopic evidence for oxygen, until 100 days after maximum light. The +100 day identification of oxygen is tentative, and would imply significant mixing of unburned or only slight processed elements down to a velocity of 6,000 km/s. Our results are in relatively good agreement with other analyses in the IR. We briefly compare SN 2011fe to SN 2014J and conclude that the differences could be due to different central densities at ignition or differences in the C/O ratio of the progenitors.

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arXiv2016

Multi-frequency studies of galaxies and groups: I. Environmental effect on galaxy stellar mass and morphology

To understand the role of the environment in galaxy formation, evolution, and present-day properties, it is essential to study the multi-frequency behavior of different galaxy populations under various environmental conditions. We crossmatch the SDSS DR10 group catalog with GAMA Data Release 2 and Wide-field Survey Explorer (WISE) data to construct a catalog of 1651 groups and 11436 galaxies containing photometric information in 15 different wavebands ranging from ultraviolet (0.152 μm) to mid-infrared (22 μm). We perform the spectral energy distribution (SED) fitting of galaxies using the MAGPHYS code and estimate the rest frame luminosities and stellar masses. We use the 1/Vmax method to estimate the galaxy stellar mass and luminosity functions, and the luminosity density field of galaxies to define the large scale environment of galaxies. The stellar mass functions of both central and satellite galaxies in groups are different in low and high density large scale environments. Satellite galaxies in high density environments have a steeper low mass end slope compared to low density environments, independently of the galaxy morphology. Central galaxies in low density environments have a steeper low mass end slope but the difference disappears for fixed galaxy morphology. The characteristic stellar mass of satellite galaxies is higher in high density environments and the difference exists only for galaxies with elliptical morphologies. Galaxy formation in groups is more efficient in high density large scale environments. Groups in high density environments have higher abundances of satellite galaxies, irrespective of the satellite galaxy morphology. The elliptical satellite galaxies are generally more massive in high density environments. The stellar masses of spiral satellite galaxies show no dependence on the large scale environment.

astro-ph.GA↗

arXiv2016

Discovery of a massive supercluster system at $z \sim 0.47$

Superclusters are the largest relatively isolated systems in the cosmic web. Using the SDSS BOSS survey we search for the largest superclusters in the redshift range $0.43<z<0.71$. We generate a luminosity-density field smoothed over $8 h^{-1}\mathrm{Mpc}$ to detect the large-scale over-density regions. Each individual over-density region is defined as single supercluster in the survey. We define the superclusters in the way that they are comparable with the superclusters found in the SDSS main survey. We found a system we call the BOSS Great Wall (BGW), which consists of two walls with diameters 186 and 173 $h^{-1}$Mpc, and two other major superclusters with diameters of 64 and 91 $h^{-1}$Mpc. As a whole, this system consists of 830 galaxies with the mean redshift 0.47. We estimate the total mass to be approximately $2\times10^{17}h^{-1}M_\odot$. The morphology of the superclusters in the BGW system is similar to the morphology of the superclusters in the Sloan Great Wall region. The BGW is one of the most extended and massive system of superclusters yet found in the Universe.

astro-ph.CO↗

arXiv2016

SN 2014J at M82: I. A middle-class type Ia supernova by all spectroscopic metrics

We present the intensive spectroscopic follow up of the type Ia supernova (SN Ia) 2014J in the starburst galaxy M82. Twenty-seven optical spectra have been acquired from January 22nd to September 1st 2014 with the Isaac Newton (INT) and William Herschel (WHT) Telescopes. After correcting the observations for the recession velocity of M82 and for Milky Way and host galaxy extinction, we measured expansion velocities from spectral line blueshifts and pseudo-equivalent width of the strongest features in the spectra, which gives an idea on how elements are distributed within the ejecta. We position SN 2014J in the Benetti (2005), Branch et al. (2006) and Wang et al. (2009) diagrams. These diagrams are based on properties of the Si II features and provide dynamical and chemical information about the SN ejecta. The nearby SN 2011fe, which showed little evidence for reddening in its host galaxy, is shown as a reference for comparisons. SN 2014J is a border-line object between the Core-normal (CN) and Broad-line (BL) groups, which corresponds to an intermediate position between Low Velocity Gradient (LVG) and High Velocity Gradient (HVG) objects. SN 2014J follows the R(Si II)-Δm15 correlation, which confirms its classification as a relatively normal SN Ia. Our description of the SN Ia in terms of the evolution of the pseudo-equivalent width of various ions as well as the position in the various diagrams put this specific SN Ia into the overall sample of SN Ia.

astro-ph.SR↗

arXiv2014

SDSS superclusters: morphology and galaxy content

We compare the galaxy populations in superclusters of different morphology in the nearby Universe (180 < d < 270 Mpc) to see whether the inner structure and overall morphology of superclusters are important in shaping galaxy properties in superclusters. Supercluster morphology has been found with Minkowski functionals. We analyse the probability density distributions of colours, morphological types, stellar masses, star formation rates (SFR) of galaxies, and the peculiar velocities of the main galaxies in groups in superclusters of filament and spider types, and in the field. We show that the fraction of red, early-type, low SFR galaxies in filament-type superclusters is higher than in spider-type superclusters; in low-density global environments their fraction is lower than in superclusters. In all environments the fraction of red, high stellar mass, and low SFR galaxies in rich groups is higher than in poor groups. In superclusters of spider morphology red, high SFR galaxies have higher stellar masses than in filament-type superclusters. Groups of equal richness host galaxies with larger stellar masses, a larger fraction of early-type and red galaxies, and a higher fraction of low SFR galaxies, if they are located in superclusters of filament morphology. The peculiar velocities of the main galaxies in groups from superclusters of filament morphology are higher than in those of spider morphology. Groups with higher peculiar velocities of their main galaxies in filament-type superclusters are located in higher density environment than those with low peculiar velocities. There are significant differences between galaxy populations of the individual richest superclusters. Therefore both local (group) and global (supercluster) environments and even supercluster morphology play an important role in the formation and evolution of galaxies.

astro-ph.CO↗

arXiv2011

Large scale environments of z<0.4 active galaxies

Properties of galaxies depend on their large-scale environment. As the influence of active galactic nuclei (AGN) in galaxy evolution is becoming more evident, their large scale environments may help us understand the evolutionary processes leading to activity. The effect of activity can be seen particularly by showing if different types of active galaxies are formed by similar mechanisms. Our aim is to study the supercluster-scale environments of active galaxies up to redshift 0.4. Our data includes quasars, BL Lac objects, Seyfert and radio galaxies. We use a three-dimensional low-resolution luminosity-density field constructed of a sample of luminous red galaxies in the seventh data release of the Sloan Digital Sky Survey. We calculate the average density of this field in a volume of a 3\,$h^{-1}$Mpc sphere around each AGN for estimating the environmental density levels of different types of AGN. This analysis gives us the distribution of AGN in the global environment of superclusters, filaments, and voids. Our results show that while radio-quiet quasars and Seyfert galaxies are mostly located in low-density regions, radio galaxies have higher environmental densities. BL Lac objects usually have low-density environments, but some of them are also in very high density regions. Our results give support to the theory of galaxy evolution where galaxies are affected by two modes of AGN feedback: quasar mode that turns a blue star-forming galaxy into a red and dead one, and radio mode that regulates the growth of massive elliptical galaxies. We conclude that quasars are in lower density environments than radio galaxies most likely because the galaxies in rich environments have evolved to a state suitable for radio-loud activity earlier. Galaxies in poor environment have evolved slower, and are still going through the earlier quasar mode feedback in galaxy evolution.

astro-ph.CO↗

arXiv2009

Environments of Nearby Quasars in Sloan Digital Sky Survey

For the first time spectroscopic galaxy redshift surveys are reaching the scales where galaxies can be studied together with the nearest quasars. This gives an opportunity to study the dependence between the activity of a quasar and its environment in a more extensive way than before. We study the spatial distribution of galaxies and groups of galaxies in the environments of low redshift quasars in the Sloan Digital Sky Survey (SDSS). Our aim is to understand how the nearby quasars are embedded in the local and global density field of galaxies and how the environment affects quasar activity. We analyse the environments of nearby quasars using number counts of galaxies. We also study the dependence of group properties to their distance to the nearest quasar. The large scale environments are studied by analysing the locations of quasars in the luminosity density field. Our study of the number counts of galaxies in quasar environments shows an underdensity of bright galaxies at a few Mpc from quasars. Also, the groups of galaxies that have a quasar closer than 2Mpc are poorer and less luminous than in average. Our analysis on the luminosity density field shows that quasars clearly avoid rich superclusters. Nearby quasars seem to be located in outskirts of superclusters or in filaments connecting them. Our results suggest that quasar evolution may be affected by density variations both on supercluster scales and in the local environment.

astro-ph.CO↗

arXiv2008

Clustering environment of BL Lac object RGB 1745+398

The BL Lac object RGB 1745+398 lies in an environment that makes it possible to study the cluster around it more deeply than the environments of other BL Lac objects. The cluster centered on the BL Lac works as a strong gravitational lens, forming a large arc around itself. The aim of this paper is to study the environment and characteristics of this object more accurately than the environments of other BL Lac objects have been before.We measured the redshifts of galaxies in the cluster from the absorption lines in their spectra. The velocity dispersion was then obtained from the redshifts. The gravitational lensing was used for measuring the mass at the center of the cluster. The mass of the whole cluster could then be estimated using the softened isothermal sphere mass distribution. Finally, the richness of the cluster was determined by counting the number of galaxies near the BL Lac object and obtaining the galaxy-BL Lac spatial covariance function, $B_{gb}$. The redshifts of nine galaxies in the field were measured to be near the redshift of the BL Lac object, confirming the presence of a cluster. The average redshift of the cluster is 0.268, and the velocity dispersion $(470^{+190}_{-110})$ km s$^{-1}$. The mass of the cluster is $M_{500}=(4^{+3}_{-2})\times10^{14} M_{\sun}$ which implies a rather massive cluster. The richness measurement also suggests that this is a rich cluster: the result for covariance function is $B_{gb}=(600\pm200)$ Mpc$^{1.77}$, which corresponds to Abell richness class 1 and which is consistent with the mass and velocity dispersion of the cluster.

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