Broad He i 1.08-µm absorption from the obscurer in the active galaxy NGC 5548

ABSTRACT The nucleus of the active galaxy NGC 5548 was the target of two intensive spectroscopic monitoring campaigns at X-ray, ultraviolet (UV), and optical frequencies in 2013/2014. These campaigns detected the presence of a massive obscuration event. In 2016/2017, Landt et al. conducted a near-IR spectroscopic monitoring campaign on NGC 5548 and discovered He i 1.08-μm absorption. Here, we decompose this absorption into its components and study its time variability. We attribute the narrow He i absorption lines to the warm absorber (WA) and, as for the newly appeared low-ionization WA lines in the UV, their presence is most likely due to a reduction in ionization parameter caused by the obscurer. The observed variability of the narrow He i absorption is consistent with what is expected for the WA. Most importantly, we also detect fast, broad He i absorption, which we attribute to the obscurer. This He i broad absorption, which is indicative of a high column density gas, is unsaturated and variable on time-scales of a few months. The observed variability of the obscurer is mainly due to changes in ionization, although density changes also play a role. We test the physical cycle model of Dehghanian et al. which proposes that helium recombination can account for how the obscurer influences the physics of the WA gas. Our results support their model, but also indicate that the reality might be more complex.

Galaxy properties in the cosmic web of EAGLE simulation

ABSTRACT We investigate the dependence of the galaxy properties on cosmic web environments using the most up-to-date hydrodynamic simulation: Evolution and Assembly of Galaxies and their Environments (EAGLE). The baryon fractions in haloes and the amplitudes of the galaxy luminosity function decrease going from knots to filaments to sheets to voids. Interestingly, the value of L* varies dramatically in different cosmic web environments. At z = 0, we find a characteristic halo mass of $10^{12}\, {\rm h}^{-1}\rm M_{\odot }$, below which the stellar-to-halo mass ratio is higher in knots, while above which it reverses. This particular halo mass corresponds to a characteristic stellar mass of $1.8\times 10^{10} \,{\rm h}^{-1}\rm M_{\odot }$. Below the characteristic stellar mass, central galaxies have redder colours, lower sSFRs, and higher metallicities in knots than those in filaments, sheets and voids, while above this characteristic stellar mass, the cosmic web environmental dependences either reverse or vanish. Such dependences can be attributed to the fact that the active galaxy fraction decreases along voids, sheets, filaments, and knots. The cosmic web dependences get weaker towards higher redshifts for most of the explored galaxy properties and scaling relations, except for the gas metallicity versus stellar mass relation.

THE ENVIRONMENTAL DEPENDENCE OF THE AGE OF ACTIVE GALAXIES AND THE DEPENDENCE OF THE CLUSTERING PROPERTIES OF ACTIVE GALAXIES ON AGE

We explore the environmental dependence of the age and the clustering-age dependence of active galaxies in two volume-limited active galaxy samples of the SDSS. In the luminous volume-limited sample, the age of active galaxies apparently depends on environments: at low density the fraction of young galaxies with ages less than 2 Gyr is significantly higher than the one in the high density case, at high density the fraction of old galaxies is significantly higher than the one at low density. Young active galaxies have a higher prevalence than old ones at small mul-tiplicity, corresponding to isolated galaxies, close pairs and small groups, whereas-old active galaxies have a higher prevalence in the multiplicity bins corresponding to dense groups and clusters. But in the faint volume-limited sample, although the environmental dependence of the age is fairly weak, a substantial clustering-age dependence can be observed.

Comoving Distance- Light Travel Distance (Treatise)

The discussion on the values of redshift, as well as blueshift, is based on a large increase in new evidence that in the whole volume of Universe there are gravitationally-bound objects (galaxies, clusters and super clusters of galaxies) „Using the Chandra and Hubble Space Telescopes we have now observed 72 collisions between galaxy clusters, including both ‘major’ and ‘minor’ mergers” (Harvey, 2015). That adds to a great diversity of galactic movement directions and their diverse appearances to an observer. The accent here is at the point of "clearing the early Universe" and asks questions about how these types of radiation could be measured if all galaxies were created in the early stages of Universe, which had started emitting these types of radiation. At the same time, some questions are asked about. With a redshift of 5.47, (Q0906 + 6930) light from this active galaxy is estimated to have taken around 12.3 billion light-years to reach us.. distance to this galaxy is estimated to be around 26 billion light-years (7961 Mpc). (NASA/IPAC, 2010) i.e., why the actual measured values of redshift are not applied.