There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

We present a catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi), during the first 11 months of the science phase of the mission, which began on 2008 August 4. The First Fermi-LAT catalog (1FGL) contains 1451 sources detected and characterized in the 100 MeV to 100 GeV range. Source detection was based on the average flux over the 11 month period, and the threshold likelihood Test Statistic is 25, corresponding to a significance of just over 4 sigma. The 1FGL catalog includes source location regions, defined in terms of elliptical fits to the 95% confidence regions and power-law spectral fits as well as flux measurements in five energy bands for each source. In addition, monthly light curves are provided. Using a protocol defined before launch we have tested for several populations of gamma-ray sources among the sources in the catalog. For individual LAT-detected sources we provide firm identifications or plausible associations with sources in other astronomical catalogs. Identifications are based on correlated variability with counterparts at other wavelengths, or on spin or orbital periodicity. For the catalogs and association criteria that we have selected, 630 of the sources are unassociated. Care was taken to characterize the sensitivity of the results to the model of interstellar diffuse gamma-ray emission used to model the bright foreground, with the result that 161 sources at low Galactic latitudes and toward bright local interstellar clouds are flagged as having properties that are strongly dependent on the model or as potentially being due to incorrectly modeled structure in the Galactic diffuse emission.

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Fermi large area telescope first source catalog

The second catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (LAT) in two years of scientific operation is presented. The second LAT AGN catalog (2LAC) includes 1017 γ-ray sources located at high Galactic latitudes (|b| > 10°) that are detected with a test statistic (TS) greater than 25 and associated statistically with AGNs. However, some of these are affected by analysis issues and some are associated with multiple AGNs. Consequently, we define a Clean Sample which includes 886 AGNs, comprising 395 BL Lacertae objects (BL Lac objects), 310 flat-spectrum radio quasars (FSRQs), 157 candidate blazars of unknown type (i.e., with broadband blazar characteristics but with no optical spectral measurement yet), 8 misaligned AGNs, 4 narrow-line Seyfert 1 (NLS1s), 10 AGNs of other types, and 2 starburst galaxies. Where possible, the blazars have been further classified based on their spectral energy distributions (SEDs) as archival radio, optical, and X-ray data permit. While almost all FSRQs have a synchrotron-peak frequency 1015 Hz. The 2LAC represents a significant improvement relative to the first LAT AGN catalog (1LAC), with 52% more associated sources. The full characterization of the newly detected sources will require more broadband data. Various properties, such as γ-ray fluxes and photon power-law spectral indices, redshifts, γ-ray luminosities, variability, and archival radio luminosities and their correlations are presented and discussed for the different blazar classes. The general trends observed in 1LAC are confirmed.

https://iopscience.iop.org/article/10.1088/0004-637X/743/2/171/pdf

The second catalog of active galactic nuclei detected by the Fermi Large Area Telescope

The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It is based on the third Fermi-LAT catalog (3FGL) of sources detected between 100 MeV and 300 GeV w ...

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The Third Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope

We present the final results from our deep Hubble Space Telescope (HST) imaging study of the host galaxies of radio-quiet quasars (RQQs), radio-loud quasars (RLQs) and radio galaxies (RGs). We describe and analyse new Wide Field & Planetary Camera 2 (WFPC2) R-band observations for 14 objects, which when combined with the first tranche of HST imaging reported in McLure et al., provide a complete and consistent set of deep, red, line-free images for statistically matched samples of 13 RQQs, 10 RLQs and 10 RGs in the redshift band 0.1 < z < 0.25. We also report the results of new deep VLA imaging that has yielded a 5-GHz detection of all but one of the 33 active galactic nuclei (AGN) in our sample.



Careful modelling of our images, aided by a high dynamic-range point spread function, has allowed us to determine accurately the morphology, luminosity, scalelength and axial ratio of every host galaxy in our sample. Armed with this information we have undertaken a detailed comparison of the properties of the hosts of these three types of powerful AGN, both internally and with the galaxy population in general.



We find that spheroidal hosts become more prevalent with increasing nuclear luminosity such that, for nuclear luminosities MV < −23.5, the hosts of both radio-loud and radio-quiet AGN are virtually all massive ellipticals. Moreover, we demonstrate that the basic properties of these hosts are indistinguishable from those of quiescent, evolved, low-redshift ellipticals of comparable mass. This result rules out the possibility that radio-loudness is determined by host-galaxy morphology, and also sets severe constraints on evolutionary schemes that attempt to link low-z ultraluminous infrared galaxies with RQQs.



Instead, we show that our results are as expected given the relationship between black hole and spheroid mass established for nearby galaxies, and apply this relation to estimate the mass of the black hole in each object. The results agree remarkably well with completely independent estimates based on nuclear emission-line widths; all the quasars in our sample have Mbh > 5 × 108 M⊙, while the radio-loud objects are confined to Mbh > 109 M⊙. This apparent mass-threshold difference, which provides a natural explanation for why RQQs outnumber RLQs by a factor of 10, appears to reflect the existence of a minimum and a maximum level of black hole radio output, which is a strong function of black hole mass (∝M2−2.5bh). Finally, we use our results to estimate the fraction of massive spheroids/black holes that produce quasar-level activity. This fraction is ≃0.1 per cent at the present day, rising to >10 per cent at z≃ 2–3.

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Quasars, their host galaxies and their central black holes

The cluster environments of powerful radio galaxies

The Robert C. Byrd Green Bank Telescope of the National Radio Astronomy Observatory is the world's premiere single-dish radio telescope operating at centimeter to long millimeter wavelengths. This paper describes the history, construction, and main technical features of the telescope.

The Green Bank Telescope

We describe phase-retrieval holography measurements of the 100-m diameter Green Bank Telescope using astronomical sources and an astronomical receiver operating at a wavelength of 7 mm. We use the technique with parameterization of the aperture in terms of Zernike polynomials and employing a large defocus, as described by Nikolic et al. (2007, AA after applying the model, the aperture efficiency is largely independent of elevation. We have also demonstrated that the technique can be used to measure and largely correct for thermal deformations of the antenna, which often exceed the uncompensated gravitational deformations during daytime observing. We conclude that the aberrations induced by gravity and thermal effects are large-scale and the technique used here is particularly suitable for measuring such deformations in large millimetre wave radio telescopes.

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Out-of-focus holography at the Green Bank Telescope

We have discovered an extreme high-velocity bipolar CO outflow in the vicinity of NGC 2023, with total outflow velocities of ~200 km s-1. At very high velocities this outflow is jetlike with an opening angle ≤4°, while it shows a separate outflow lobe at low velocities. The outflow is bipolar and exhibits a clear mirror symmetry, which suggests that the source powering the outflow is episodic or precessing. The dynamical timescales for the outflow are ≤3000 yr. We identify the source driving the CO jet with a deeply embedded low-luminosity submillimeter double source (separation ~23''), where the primary component lies on the symmetry axis of the outflow and has all the signatures of a "class 0" protostellar object. Analysis of molecular data and (sub)millimeter photometry suggests that the driving source is cold and compact, with a luminosity of lesssim10 L☉ and a total mass of 1.8-4.6 M☉. It has no near-IR counterpart, it drives an extremely young outflow, and it emits a large fraction of its luminosity in the submillimeter regime. Both millimeter sources have low dust emissivity, β ~ 0.8-1.3, similar to what is found for other class 0 objects, while the surrounding molecular cloud core appears to have a β ~ 2.0, the canonical value for "normal" interstellar dust in the submillimeter regime.

/pdf/a-jet-driven-extreme-high-velocity-outflow-powered-by-a-cold-3g713w1bib.pdf

A Jet-driven, Extreme High-Velocity Outflow Powered by a Cold, Low-Luminosity Protostar near NGC 2023

Etude basee sur les images CCD d'un echantillon de 31 radiogalaxies puissantes avec z<0,25 de l'hemisphere austral

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Richard M. Prestage

Papers

The cluster environments of powerful radio galaxies

The Green Bank Telescope

Out-of-focus holography at the Green Bank Telescope

A Jet-driven, Extreme High-Velocity Outflow Powered by a Cold, Low-Luminosity Protostar near NGC 2023

Surface photometry of powerful radio galaxies. II: Relations with the radio, optical, and clustering properties