On the dichotomy of Seyfert 2 galaxies: intrinsic differences and evolution

We present a study of the local environment (<200 kpc/h) of 31 Hidden Broad Line Region (HBLR) and 43 non-HBLR Seyfert 2 galaxies (Sy2) in the nearby universe (z<0.04). To compare our findings, we constructed two control samples that match the redshift and the morphological type distribution of the HBLR and non-HBLR samples respectively. We used the NED (NASA extragalactic database) to find all neighboring galaxies within projected radius of 200 kpc/h around each galaxy, and radial velocity difference delta_u< 500 km/s. We find that, within a projected radius of at least 150 kpc/h around each Seyfert, the fraction of non-HBLR Sy2 galaxies with a close companion is significantly higher than that of their control sample, at the 96% confidence level. Interestingly, the difference is due to the high frequency of mergers in the non-HBLR sample, seven versus only one in the control sample, while also they present a high number of hosts with signs of peculiar morphology. In sharp contrast, the HBLR sample is consistent with its control sample and furthermore, the number of their host galaxies that present peculiar morphology, which probably implies some level of interactions or merging in the past, is the lowest in all four galaxy samples. Given that the HBLR Seyfert 2 galaxies are essentially Seyfert 1 (Sy1), with their broad line region (BLR) hidden because of the obscuration by the torus, while the non-HBLR Sy2 sample probably also includes intrinsically different objects, like "true" Sy2s that lack the BLR, and heavily obscured objects that prohibit even its indirect detection, our results are discussed within the context of an evolutionary sequence of activity triggered by close galaxy interactions and merging. We argue that the non-HBLR Sy2 galaxies may represent different stages of this sequence, possibly the beginning and the end of the nuclear activity.Comment: 9 pages, published by A&

HENLEOVA PETLJA KAO PREKRETNICA SPOSOBNOSTI KONCENTRIRANJA BUBREGA SISAVACA: POVIJESNI PREGLED

The first description of the renal tubules is attributed to Lorenzo Bellini in 1662 and four years later Marcello Malpighi described the glomerulus. In 1842 Sir William Bowman described the capsule that surrounds the Malpighian body and its connection with the renal tubule and introduced the “excretory” hypothesis of urine formation. In the same year, Carl Ludwig introduced the “filtration-reabsorption” hypothesis of urine formation. Bowman’s hypothesis was accepted by the so-called “vitalists” and Ludwig’s hypothesis by the so-called “mechanists”. In the middle of this confliction, Jacob Henle described in 1862 the homonymous “U” shaped loop but his discovery has neglected. In 1942 Werner Kuhn, a physical chemist, proposed that the loop of Henle may be the natural analog of the hairpin countercurrent multiplication system which concentrates urine in mammalian kidneys. In 1951 Kuhn, Hargitay and Wirz showed experimentally that the loop of Henle was the most important part of the countercurrent multiplication system of urine-concentrating mechanism in mammalian kidneys. The new theory was accepted by English-speaking scientists later, in 1958, when Carl Gottschalk and Margaret Mylle published their experimental work and proved that Kuhn’s theory was correct. Gottschalk summarized the evidence of the accumulated knowledge in 1962, three centuries after the first description of renal tubules and one century after description of Henle’s loop.Prvi se opis bubrežnih tubula iz 1662. pripisuje Lorenzu Belliniju, a četiri je godine kasnije Marcello Malpighi opisao glomerul. Godine 1842. je Sir William Bowman opisao kapsulu koja okružuje malpigijevo tjelešce i njegovu vezu s bubrežnim tubulima te uveo “ekskretornu” hipotezu o stvaranju urina. Iste je godine Carl Ludwig uveo je “filtracijsko‑reasorpcijsku” hipotezu stvaranja urina. Bowmanova je hipoteza bila prihvaćena od strane tzv. “vitalista”, a Ludwigova hipoteza od strane tzv. “mehanicista”. U jeku tog sukoba Jakob Henle opisao je 1862. homonimne petlje u obliku slova “U”, ali njegovo je otkriće zanemareno. Godine 1942. je Werner Kuhn, fizikalni kemičar, predložio ideju da je Henleova petlja možda prirodni analogon kopče protustrujnog multiplikacijskog sustava koji koncentrira urin u bubrezima sisavaca. Godine su 1951. Kuhn, Hargitay i Wirz eksperimentalno pokazali da da je Henleova petlja najvažniji dio protustrujnog multiplikacijskog sustava mehanizma za koncentriranje urina u bubrezima sisavaca. Nova je teorija prihvaćena od strane anglofonih znanstvenika kasnije, 1958. godine, kada su Carl Gottschalk i Margaret Mylle objavili svoj eksperimentalni rad i dokazali da je Kuhnova teorija bila točna. Gottschalk je sažeo dokaze sakupljenog znanja 1962., tri stoljeća nakon prvog opisa bubrežnih tubula i jednog stoljeća nakon opisa Henleove petlje

Luminous X-ray AGN in Clusters of Galaxies

We present a study of X-ray AGN overdensities in 16 Abell clusters, within the redshift range 0.073<z<0.279, in order to investigate the effect of the hot inter-cluster environment on the triggering of the AGN phenomenon. The X-ray AGN overdensities, with respect to the field expectations, were estimated for sources with L_x>= 10^{42} erg s^{-1} (at the redshift of the clusters) and within an area of 1 h^{-1}_{72} Mpc radius (excluding the core). To investigate the presence or not of a true enhancement of luminous X-ray AGN in the cluster area, we also derived the corresponding optical galaxy overdensities, using a suitable range of $r$-band magnitudes. We always find the latter to be significantly higher (and only in two cases roughly equal) with respect to the corresponding X-ray overdensities. Over the whole cluster sample, the mean X-ray point-source overdensity is a factor of ~4 less than that corresponding to bright optical galaxies, a difference which is significant at a >0.995 level, as indicated by an appropriate t-student test. We conclude that the triggering of luminous X-ray AGN in rich clusters is strongly suppressed. Furthermore, searching for optical SDSS counterparts of all the X-ray sources, associated with our clusters, we found that about half appear to be background QSOs, while others are background and foreground AGN or stars. The true overdensity of X-ray point sources, associated to the clusters, is therefore even smaller than what our statistical approach revealed.Comment: accepted for publication in ApJ Letter

A novel 1.5 '' quadruple antenna for tri-band GPS applications

A new global positioning system (GPS) antenna is proposed to cover the three GPS bands (L1, L2, and L5, namely 1575, 1227, and 1176 MHz) with the L5 band to be added after 2006. The developed antenna size is only 1.5" x 1.5" in aperture corresponding to lambda/7 x lambda/7 (lambda = free space wavelength) and lambda/13 thick. Quadrature feeding is employed to ensure right-hand circular polarized (RHCP) radiation. The final miniature antenna exhibits a gain greater than 2 dBi, and to our knowledge this is the smallest such size for circular polarized (CP) operation covering all three bands. Detailed parametric simulations leading to the best design along with measurements for the constructed antenna are presented

HENLEOVA PETLJA KAO PREKRETNICA SPOSOBNOSTI KONCENTRIRANJA BUBREGA SISAVACA: POVIJESNI PREGLED

The first description of the renal tubules is attributed to Lorenzo Bellini in 1662 and four years later Marcello Malpighi described the glomerulus. In 1842 Sir William Bowman described the capsule that surrounds the Malpighian body and its connection with the renal tubule and introduced the “excretory” hypothesis of urine formation. In the same year, Carl Ludwig introduced the “filtration-reabsorption” hypothesis of urine formation. Bowman’s hypothesis was accepted by the so-called “vitalists” and Ludwig’s hypothesis by the so-called “mechanists”. In the middle of this confliction, Jacob Henle described in 1862 the homonymous “U” shaped loop but his discovery has neglected. In 1942 Werner Kuhn, a physical chemist, proposed that the loop of Henle may be the natural analog of the hairpin countercurrent multiplication system which concentrates urine in mammalian kidneys. In 1951 Kuhn, Hargitay and Wirz showed experimentally that the loop of Henle was the most important part of the countercurrent multiplication system of urine-concentrating mechanism in mammalian kidneys. The new theory was accepted by English-speaking scientists later, in 1958, when Carl Gottschalk and Margaret Mylle published their experimental work and proved that Kuhn’s theory was correct. Gottschalk summarized the evidence of the accumulated knowledge in 1962, three centuries after the first description of renal tubules and one century after description of Henle’s loop.Prvi se opis bubrežnih tubula iz 1662. pripisuje Lorenzu Belliniju, a četiri je godine kasnije Marcello Malpighi opisao glomerul. Godine 1842. je Sir William Bowman opisao kapsulu koja okružuje malpigijevo tjelešce i njegovu vezu s bubrežnim tubulima te uveo “ekskretornu” hipotezu o stvaranju urina. Iste je godine Carl Ludwig uveo je “filtracijsko‑reasorpcijsku” hipotezu stvaranja urina. Bowmanova je hipoteza bila prihvaćena od strane tzv. “vitalista”, a Ludwigova hipoteza od strane tzv. “mehanicista”. U jeku tog sukoba Jakob Henle opisao je 1862. homonimne petlje u obliku slova “U”, ali njegovo je otkriće zanemareno. Godine 1942. je Werner Kuhn, fizikalni kemičar, predložio ideju da je Henleova petlja možda prirodni analogon kopče protustrujnog multiplikacijskog sustava koji koncentrira urin u bubrezima sisavaca. Godine su 1951. Kuhn, Hargitay i Wirz eksperimentalno pokazali da da je Henleova petlja najvažniji dio protustrujnog multiplikacijskog sustava mehanizma za koncentriranje urina u bubrezima sisavaca. Nova je teorija prihvaćena od strane anglofonih znanstvenika kasnije, 1958. godine, kada su Carl Gottschalk i Margaret Mylle objavili svoj eksperimentalni rad i dokazali da je Kuhnova teorija bila točna. Gottschalk je sažeo dokaze sakupljenog znanja 1962., tri stoljeća nakon prvog opisa bubrežnih tubula i jednog stoljeća nakon opisa Henleove petlje

The Environment of HII Galaxies revisited

We present a study of the close (< 200 kpc) environment of 110 relatively local (z< 0.16) HII galaxies, selected from the Sloan Digital Sky Survey (SDSS; DR7). We use available spectroscopic and photometric redshifts in order to investigate the presence of a close and possibly interacting companion galaxy. Our aim is to compare the physical properties of isolated and interacting HII galaxies and investigate possible systematic effects in their use as cosmological probes. We find that interacting HII galaxies tend to be more compact, less luminous and have a lower velocity dispersion than isolated ones, in agreement with previous studies on smaller samples. However, as we verified, these environmental differences do not affect the cosmologically important L_{H{\beta}}-{\sigma} correlation of the HII galaxies.Comment: 5 pages, accepted for publication in A&

The XMM-Newton Needles in the Haystack Survey: the local X-ray luminosity function of 'normal' galaxies

In this paper we estimate the local (z<0.22) X-ray luminosity function of `normal' galaxies derived from the XMM-Newton Needles in the Haystack Survey. This is an on-going project that aims to identify X-ray selected `normal' galaxies (i.e. non-AGN dominated) in the local Universe. We are using a total of 70 XMM-Newton fields covering an area of 11 sq. degrees which overlap with the Sloan Digital Sky Survey Data Release-2. `Normal' galaxies are selected on the basis of their resolved optical light profile, their low X-ray--to--optical flux ratio (log(f_x/f_o)<-2) and soft X-ray colours. We find a total of 28 candidate `normal' galaxies to the 0.5-8 keV band flux limit of ~2x10^{-15} cgs. Optical spectra are available for most sources in our sample (82 per cent). These provide additional evidence that our sources are bona-fide 'normal' galaxies with X-ray emission coming from diffuse hot gas emission and/or X-ray binaries rather than a supermassive black hole. Sixteen of our galaxies have narrow emission lines or a late-type Spectral Energy Distribution (SED) while the remaining 12 present only absorption lines or an early-type SED. Combining our XMM-Newton sample with 18 local (z<0.22) galaxies from the Chandra Deep Field North and South surveys, we construct the local X-ray luminosity function of `normal' galaxies. This can be represented with a Schechter form with a break at L* ~ 3x10^{41} cgs and a slope of ~1.78+/-0.12. Using this luminosity function and assuming pure luminosity evolution of the form (1+z)^{3.3} we estimate a contribution to the X-ray background from `normal' galaxies of 10-20 per cent (0.5-8 keV). Finally, we derive, for the first time, the luminosity functions for early and late type systems separately.Comment: To appear to MNRAS, 9 page

X-ray AGN in the XMM-LSS galaxy clusters: no evidence of AGN suppression

We present a study of the overdensity of X-ray selected AGN in 33 galaxy clusters in the XMM-LSS field, up to redhift z=1.05. Previous studies have shown that the presence of X-ray selected AGN in rich galaxy clusters is suppressed. In the current study we investigate the occurrence of X-ray selected AGN in low and moderate X-ray luminosity galaxy clusters. Due to the wide contiguous XMM-LSS survey area we are able to extend the study to the cluster outskirts. We therefore determine the projected overdensity of X-ray point-like sources out to 6r_{500} radius. To provide robust statistical results we also use a stacking analysis of the cluster projected overdensities. We investigate whether the observed X-ray overdensities are to be expected by estimating also the corresponding optical galaxy overdensities. We find a positive X-ray projected overdensity at the first radial bin, which is however of the same amplitude as that of optical galaxies. Therefore, no suppression of X-ray AGN activity with respect to the field is found, implying that the mechanisms responsible for the suppression are not so effective in lower density environments. After a drop to roughly the background level between 2 and 3r_{500}, the X-ray overdensity exhibits a rise at larger radii, significantly larger than the corresponding optical overdensity. Finally, using redshift information of all optical counterparts, we derive the spatial overdensity profile of the clusters. We find that the agreement between X-ray and optical overdensities in the first radial bin is also suggested in the 3-dimensional analysis. However, we argue that the X-ray overdensity "bump" at larger radial distance is probably a result of flux boosting by gravitational lensing of background QSOs. For high redshift clusters an enhancement of X-ray AGN activity in their outskirts is still possible.Comment: 16 pages. Accepted for publication in A&

Host galaxy and orientation differences between different types of AGN

The main purpose of this study is to investigate aspects regarding the validity of the AGN unification paradigm (UP). In particular we focus on the AGN host galaxies, which according to the UP should show no systematic differences depending on the AGN classification. For the purpose of this study we use (a) the spectroscopic SDSS (Sloan Digital Sky Survey) DR14 catalogue, in order to select and classify AGNs using emission line diagnostics, up to a redshift of z=0.2, and (b) the Galaxy Zoo Project catalogue, which classifies SDSS galaxies in two broad Hubble types, spirals and ellipticals. We find that the fraction of type-1 Seyfert nuclei (Sy1) hosted in elliptical galaxies is significantly larger than the corresponding fraction of any other AGN type, while there is a gradient of increasing Spiral-hosts from Sy1 to Liner, type-2 Seyferts (Sy2) and Composite nuclei. These findings cannot be interpreted within the standard Unification Paradigm, but possibly by a co-evolution scheme for supermassive black holes (SMBH) and galactic bulges. Furthermore, for the case of spiral host galaxies we find the Sy1 population to be strongly skewed towards face-on configurations, while the corresponding Sy2 population range in all host-galaxy orientation configurations, having a similar, but not identical, orientation distribution with star-forming galaxies (SF). These results also cannot be interpreted by the standard Unification Paradigm, but point towards a significant contribution of the galactic disk to the obscuration of the nuclear region. This is also consistent with the observed preference of Sy1 nuclei to be hosted by ellipticals, ie., the dusty disk of spiral hosts contributes to the obscuration of the broad line region (BLR) and thus relatively more ellipticals are expected to appear hosting Sy1 nuclei.Comment: 8 pages, 12 figure