اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدDetermining the core radio luminosity function of radio AGNs via copula
77
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The radio luminosity functions (RLFs) of active galactic nuclei (AGNs) are traditionally measured based on total emission, which doesnt reflect the current activity of the central black hole. The increasing interest in compact radio cores of AGNs requires determination of the RLF based on core emission (i.e., core RLF). In this work we have established a large sample (totaling 1207) of radio-loud AGNs, mainly consisting of radio galaxies (RGs) and steep-spectrum radio quasars (SSRQs). Based on the sample, we explore the relationship between core luminosity ($L_c$) and total luminosity ($L_t$) via a powerful statistical tool called Copula. The conditional probability distribution $p(log L_{c} mid log L_{t})$ is obtained. We derive the core RLF as a convolution of $p(log L_{c} mid log L_{t})$ with the total RLF which was determined by previous work. We relate the separate RG and SSRQ core RLFs via a relativistic beaming model and find that SSRQs have an average Lorentz factor of $gamma=9.84_{-2.50}^{+3.61}$, and that most are seen within $8^{circ} lesssim theta lesssim 45^{circ}$ of the jet axis. Compared with the total RLF which is mainly contributed by extended emission, the core RLF shows a very weak luminosity-dependent evolution, with the number density peaking around $zthicksim 0.8$ for all luminosities. Differences between core and total RLFs can be explained in a framework involving a combination of density and luminosity evolutions where the cores have significantly weaker luminosity evolution than the extended emission.
قيم البحث
اقرأ أيضاً
We assemble a large set of 2-10 GHz radio flux density measurements and upper limits of 294 different supernovae (SNe), from the literature and our own and archival data. Only 31% of the SNe were detected. We characterize the SN lightcurves near the
peak using a two-parameter model, with $t_{rm pk}$ being the time to rise to a peak and $L_{rm pk}$ the spectral luminosity at that peak. Over all SNe in our sample at $D<100$ Mpc, we find that $t_{rm pk} = 10^{1.7pm0.9}$ d, and that $L_{rm pk} = 10^{25.5pm1.6}$ erg s$^{-1}$ Hz$^{-1}$, and therefore that generally, 50% of SNe will have $L_{rm pk} < 10^{25.5}$ erg s$^{-1}$ Hz$^{-1}$. These $L_{rm pk}$ values are ~30 times lower than those for only detected SNe. Types I b/c and II (excluding IIns) have similar mean values of $L_{rm pk}$ but the former have a wider range, whereas Type IIn SNe have ~10 times higher values with $L_{rm pk} = 10^{26.5pm1.1}$ erg s$^{-1}$ Hz$^{-1}$. As for $t_{rm pk}$, Type I b/c have $t_{rm pk}$ of only $10^{1.1pm0.5}$ d while Type II have $t_{rm pk} = 10^{1.6pm1.0}$ and Type IIn the longest timescales with $t_{rm pk} = 10^{3.1pm0.7}$ d. We also estimate the distribution of progenitor mass-loss rates, $dot M$, and find the mean and standard deviation of log$_{10}(dot M/$Msol) yr$^{-1}$ are $-5.4pm1.2$ (assuming $v_{rm wind}=1000$ km s$^{-1}$) for Type I~b/c SNe, and $-6.9pm1.4$ (assuming $v_{rm wind} = 10$ km s$^{-1}$ for Type II SNe excluding Type IIn.
By cross-matching the currently largest optical catalog of galaxy clusters and the NVSS radio survey database, we obtain the largest complete sample of brightest cluster galaxies (BCGs) in the redshift range of 0.05<z<0.45, which have radio emission
and redshift information. We confirm that more powerful radio BCGs tend to be these optically very bight galaxies located in more relaxed clusters. We derived the radio luminosity functions of BCGs from the largest complete sample of BCGs, and find that the functions depend on the optical luminosity of BCGs and the dynamical state of galaxy clusters. However, the radio luminosity function does not show significant evolution with redshift.
Active galactic nuclei (AGNs) are known to cover an extremely broad range of radio luminosities and the spread of their radio-loudness is very large at any value of the Eddington ratio. This implies very diverse jet production efficiencies which can
result from the spread of the black hole spins and magnetic fluxes. Magnetic fluxes can be developed stochastically in the innermost zones of accretion discs, or can be advected to the central regions prior to the AGN phase. In the latter case there could be systematic differences between the properties of galaxies hosting radio-loud (RL) and radio-quiet (RQ) AGNs. In the former case the differences should be negligible for objects having the same Eddington ratio. To study the problem we decided to conduct a comparison study of host galaxy properties of RL and RQ AGNs. In this study we selected type II AGNs from SDSS spectroscopic catalogues. Our RL AGN sample consists of the AGNs appearing in the Best & Heckman (2012) catalogue of radio galaxies. To compare RL and RQ galaxies that have the same AGN parameters we matched the galaxies in black hole mass, Eddington ratio and redshift. We compared several properties of the host galaxies in these two groups of objects like galaxy mass, colour, concentration index, line widths, morphological type and interaction signatures. We found that in the studied group RL AGNs are preferentially hosted by elliptical galaxies while RQ ones are hosted by galaxies of later type. We also found that the fraction of interacting galaxies is the same in both groups of AGNs. These results suggest that the magnetic flux in RL AGNs is advected to the nucleus prior to the AGN phase.
We have re-analyzed continuum and recombination lines radio data available in the literature in order to derive the luminosity function (LF) of Galactic HII regions. The study is performed by considering the first and fourth Galactic quadrants indepe
ndently. We estimate the completeness level of the sample in the fourth quadrant at 5 Jy, and the one in the first quadrant at 2 Jy. We show that the two samples (fourth or first quadrant) include, as well as giant and super-giant HII regions, a significant number of sub-giant sources. The LF is obtained, in each Galactic quadrant, with a generalized Schmidts estimator using an effective volume derived from the observed spatial distribution of the considered HII regions. The re-analysis also takes advantage of recently published ancillary absorption data allowing to solve the distance ambiguity for several objects. A single power-law fit to the LFs retrieves a slope equal to -2.23+/-0.07 (fourth quadrant) and to -1.85+/-0.11 (first quadrant). We also find marginal evidence of a luminosity break at L_knee = 10^23.45 erg s^(-1) Hz^(-1) for the LF in the fourth quadrant. We convert radio luminosities into equivalent H_alpha and Lyman continuum luminosities to facilitate comparisons with extra-galactic studies. We obtain an average total HII regions Lyman continuum luminosity of 0.89 +/- 0.23 * 10^(53) sec^(-1), corresponding to 30% of the total ionizing luminosity of the Galaxy.
We compare the optical properties of the host galaxies of radio-quiet (RQ) and radio-loud (RL) Type 2 active galactic nuclei (AGNs) to infer whether the jet production efficiency depends on the host properties or is determined just by intrinsic prope
rties of the accretion flows. We carefully select galaxies from SDSS, FIRST, and NVSS catalogs. We confirm previous findings that the fraction of RL AGNs depends on the black-hole (BH) masses, and on the Eddington ratio. The comparison of the nature of the hosts of RL and RQ AGNs, therefore, requires pair-matching techniques. Matching in BH mass and Eddington ratio allows us to study the differences between galaxies hosting RL and RQ AGNs that have the same basic accretion parameters. We show that these two samples differ predominantly in the host-galaxy concentration index, morphological type (in the RL sample the frequency of elliptical galaxies becoming larger with increasing radio loudness), and nebular extinction (galaxies with highest radio loudness showing only low nebular extinction). Contrary to some previous studies, we find no significant difference between our radio-loud and radio-quiet samples regarding merger/interaction features.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
