Interferometric Monitoring of Gamma-ray Bright AGNs: OJ 287
Jee Won Lee, Sang-Sung Lee, Juan-Carlos Algaba, Jeffrey Hodgson, Jae-Young Kim, Jongho Park, Motoki Kino, Dae-Won Kim, Sincheol Kang, Sungmin Yoo, Sang Hyun Kim, Mark Gurwell
备注：
27 pages, 9 figures, Accepted for publication in ApJ
We present the results of simultaneous multi-frequency imaging observations at 22, 43, 86, and 129\,GHz of OJ\,287. We used the Korean VLBI Network as part of the Interferometric MOnitoring of GAmma-ray Bright active galactic nuclei (iMOGABA). The iMOGABA observations were performed during 31 epochs from 2013 January 16 to 2016 December 28. We also used 15\,GHz OVRO and 225\,GHz SMA flux density data. We analyzed four flux enhancements in the light curves. The estimated time scales of three flux enhancements were similar with time scales of $\sim$50 days at two frequencies. A fourth flux enhancement had a variability timescale approximately twice as long. We found that 225\,GHz enhancements led the 15\,GHz enhancements by a range of 7 to 30 days in the time delay analysis. We found the fractional variability did not change with frequency between 43 and 86\,GHz. We could reliably measure the turnover frequency, $ν_{\rm c}$, of the core of the source in three epochs. This was measured to be in a range from 27 to 50\,GHz and a flux density at the turnover frequency, $S_{\rm m}$, ranging from 3-6\,Jy. The derived SSA magnetic fields, $B_{\rm SSA}$, are in a range from $0.157\pm0.104$ to $0.255\pm0.146$ mG. We estimated the equipartition magnetic field strengths to be in a range from $0.95\pm0.15$ to $1.93\pm0.30$ mG. The equipartition magnetic field strengths are up to a factor of 10 higher than the values of $B_{\rm SSA}$. We conclude that the downstream jet may be more particle energy dominated.
We present the results of multi-epoch, multi-frequency monitoring of a blazar 4C +29.45, which was regularly monitored as part of the Interferometric Monitoring of GAmma-ray Bright Active Galactic Nuclei (iMOGABA) program - a key science program of the Korean Very long baseline interferometry Network (KVN). Observations were conducted simultaneously at 22, 43, 86, and 129 GHz during the 4 years from 5 December 2012 to 28 December 2016. We also used additional data from the 15 GHz Owens Valley Radio Observatory (OVRO) monitoring program. From the 15 GHz light curve, we estimated the variability…
Many X-ray bright active galactic nuclei (AGN) are predicted to follow an extended stage of obscured black hole growth. In support of this picture we examine the X-ray undetected AGNs in the COSMOS field and compare their host galaxies with X-ray bright AGNs. We examine galaxies with M_\ast>10^{9.5}M_\odot for the presence of AGNs at redshifts $z=0.5-3$. We select AGNs in the infrared using \textit{Spitzer} and \textit{Herschel} detections and use color selection techniques to select AGNs within strongly star forming hosts. We stack \textit{Chandra} X-ray data of galaxies with an IR detection …
Discovery of ultra-fast outflows with v$_{\rm out}>0.3 \rm c$ in local bright active galactic nuclei
Università di Bologna（博洛尼亚大学）；INAF – OAS, Osservatorio di Astrofisica e Scienza dello Spazio Bologna（意大利国家天体物理研究所-波伦亚天文与空间科学观测站）；European Space Agency (ESA)（欧洲航天局）；European Space Research and Technology Centre (ESTEC)（欧洲航天研究与技术中心）；INAF – Osservatorio Astronomico di Roma（意大利国家天体物理研究所-罗马天文台）；INAF – Istituto di Astrofisica e Planetologia Spaziali（意大利国家天体物理研究所-空间天体物理学与行星科学研究所）；Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）
X-ray emission detection in a galaxy is one of the efficient tools for selecting Active Galactic Nuclei (AGNs). However, many X-ray-selected AGNs are not easily selected as AGNs by their optical emission. These galaxies, so-called optically dull (OD) AGNs, are fascinating since their X-ray emission is bright even though the AGN signature in the optical regime is absent. In a deep multiwavelength survey over 2 deg$^2$ of the Cosmic Evolution Survey (COSMOS) field, we have looked for the OD AGNs using photometric, spectroscopic, and X-ray data. We identified 310 non-broad line sources with optic…
Reverberation mapping (RM) is an efficient method to investigate the physical sizes of the broad line region (BLR) and dusty torus in an active galactic nucleus (AGN). The Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) mission will provide multi-epoch spectroscopic data at optical and near-infrared wavelengths. These data can be used for RM experiments for bright AGNs. We present results of a feasibility test using SPHEREx data in the SPHEREx deep regions for the torus RM measurements. We investigate the physical properties of bright AGNs …
Using $I$-band images of 35 nearby ($z<0.1$) type 1 active galactic nuclei (AGNs) obtained with Hubble Space Telescope, selected from the 70-month Swift-BAT X-ray source catalog, we investigate the photometric properties of the host galaxies. With a careful treatment of the point-spread function (PSF) model and imaging decomposition, we robustly measure the $I$-band brightness and the effective radius of bulges in our sample. Along with black hole (BH) mass estimates from single-epoch spectroscopic data, we present the relation between BH mass and $I$-band bulge luminosity ($M_{\rm BH}-M_{I,\r…
The direction of parsec-scale jets in active galactic nuclei (AGNs) is essential information for many astrophysical and astrometric studies, including linear polarization and magnetic field structure, frequency-dependent synchrotron opacity, proper motion, and reference frame alignment. We developed a rigorous, simple, and completely automated method to measure the directions from calibrated interferometric visibility data at frequencies ranging from 1.4 GHz to 86 GHz. We publish the results for 9220 AGNs with the typical accuracy below 10 degrees. An internal check of the method comparing the…
Radio-Loud (RL) Active Galactic Nuclei (AGNs) are among the brightest astrophysical sources at all wavelengths. Their relativistic jets can affect both their Supermassive Black Holes (SMBHs) growth and the surrounding intergalactic medium. While in the radio band these jets can be observed at all scales (from pc to Mpc scales), their X-ray and γ-ray emission is expected to be concentrated on very small scales (<10 pc). However, after the launch of the Chandra X-ray telescope, several kpc-scale jets were detected and the mechanism responsible for their high-energy radiation at these scales is s…
Studies of the high-redshift rest-frame ultraviolet (UV) luminosity functions (LFs) have typically treated the star-forming galaxy and active galactic nuclei (AGN) populations separately, as they have different survey depth and area requirements. However, the recent advent of wide-area deep ground-based imaging surveys now probe volumes large enough to discover AGNs, at depths sensitive enough for fainter star-forming galaxies, bridging these two populations. Using results from such surveys as observational constraints, we present a methodology to jointly empirically model the evolution of the…
Most baryonic matter in the universe exists in gaseous form and can be found in structures such as galactic halos and the low-density intergalactic medium. proposed-ray spectroscopy missions such as Athena, Arcus, and Lynx will have the capability to identify absorption lines in spectra toward bright active galactic nuclei (AGNs), which can be used as a tool to probe this missing matter. In this study, we examine the optical fields surrounding 15 primary observing targets and identify the foreground galaxies and galaxy groups that are potential hosts of absorption. We record the basic properti…
We present a study of the 1173 sources brighter than $S_{1.4\,\rm GHz}= 120\,μ$Jy detected over an area of $\simeq 1.4\,\hbox{deg}^{2}$ in the Lockman Hole field. Exploiting the multi-band information available in this field for $\sim$79% of the sample, sources have been classified into radio loud (RL) active galactic nuclei (AGNs), star forming galaxies (SFGs) and radio quiet (RQ) AGNs, using a variety of diagnostics available in the literature. Exploiting the observed tight anti-correlations between IRAC band 1 or band 2 and the source redshift we could assign a redshift to 177 sources missi…
High redshift AGNs and HI reionisation: limits from the unresolved X-ray background
z~3处明亮类星体数量的迅速减少似乎对HI莱曼极限的电离背景的贡献越来越小。因此，一般认为（前）星系系统中的大质量恒星可能提供额外的电离通量，以在z>6时完成HI再电离。然而，一个星系主导的背景，可能需要从高红移星系的莱曼连续辐射的逃逸分数高达10%，一个值有点不一致（公认的稀缺）的观测约束。矮星系的高逃逸分数一直被提倡，或者，一个迄今未被发现（或几乎未被发现）的人口的无遮蔽，高红移微弱AGN。在这里，我们质疑后者的假设，并表明，这样的来源，是一致的，在z=0的未解决的X射线背景的测量水平，可以提供一个分数的HII填充因子不大于13%的z=6。分数上升到<27% in the somewhat extreme case of a constant comoving redshift evolution of the AGN emissivity. This still calls for a mean escape fraction of ionising photons from high-z galaxies >10%。
