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

We present an incremental version (4FGL-DR2, for Data Release 2) of the fourth Fermi-LAT catalog of gamma-ray sources. Based on the first ten years of science data in the energy range from 50 MeV to 1 TeV, it uses the same analysis methods as the 4FGL catalog did for eight years of data. The spectral parameters, spectral energy distributions and associations are updated for all sources. Light curves are rebuilt for all sources with 1-year intervals (not 2-month intervals). Among the 5064 4FGL sources, 120 are formally below the detection threshold over 10 years (but are kept in the list), while 40 are newly associated. We report 723 new sources, mostly just above the detection threshold, among which two are considered identified and 342 have a plausible counterpart at other wavelengths.

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Fermi Large Area Telescope Fourth Source Catalog Data Release 2

(Abridged) Studying continuum emission from interstellar dust is essential to locate and characterize the highest density regions in the interstellar medium. In particular, the early stages of massive star formation are still mysterious. Our goal is to produce a large scale, systematic database of massive pre- and proto-stellar clumps in the Galaxy, in order to better understand how and under what conditions star formation takes place. A well characterized sample of star-forming sites will deliver an evolutionary sequence and a mass function of high-mass star-forming clumps. Such a systematic survey at submm wavelengths also represents a pioneering work in preparation for Herschel and ALMA. The APEX telescope is ideally located to observe the inner Milky Way. The recently commissioned Large APEX Bolometer Camera (LABOCA) is a 295-element bolometer array observing at 870 microns, with a beam of 19". Taking advantage of its large field of view (11.4') and excellent sensitivity, we have started an unbiased survey of the Galactic Plane, with a noise level of 50-70 mJy/beam: the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). As a first step, we have covered 95 sq. deg. These data reveal 6000 compact sources brighter than 0.25 Jy, as well as extended structures, many of them filamentary. About two thirds of the compact sources have no bright infrared counterpart, and some of them are likely to correspond to the precursors of (high-mass) proto-stars or proto-clusters. Other compact sources harbor hot cores, compact HII regions or young embedded clusters. Assuming a typical distance of 5 kpc, most sources are clumps smaller than 1 pc with masses from a few 10 to a few 100 M_sun. In this introductory paper, we show preliminary results from these ongoing observations, and discuss the perspectives of the survey.

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ATLASGAL - The APEX Telescope Large Area Survey of the Galaxy at 870 microns

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

This paper is the second in a series describing the Sydney University Molonglo Sky Survey (SUMSS) being carried out at 843 MHz with the Molonglo Observatory Synthesis Telescope (MOST). The survey will consist of ∼590 4.3° x 4.3° mosaic images with 45 x 45 cosec‖δ‖ arcsec 2 resolution, and a source catalogue. In this paper we describe the initial release (version 1.0) of the source catalogue consisting of 107 765 radio sources made by fitting elliptical Gaussians in 271 SUMSS 4.3° × 4.3° mosaics to a limiting peak brightness of 6 mJy beam - 1 at δ ≤ -50° and 10 mJy beam - 1 at δ > -50°. The catalogue covers approximately 3500 deg 2 of the southern sky with δ ≤ -30°, about 43 per cent of the total survey area. Positions in the catalogue are accurate to within 1-2 arcsec for sources with peak brightness A 8 4 3 ≥ 20 mJy beam - 1 and are always better than 10 arcsec. The internal flux density scale is accurate to within 3 per cent. Image artefacts have been classified using a decision tree, which correctly identifies and rejects spurious sources in over 96 per cent of cases. Analysis of the catalogue shows that it is highly uniform and is complete to 8 mJy at δ ≤ -50° and 18 mJy at δ > -50°. In this release of the catalogue about 7000 sources are found in the overlap region with the National Radio Astronomy Observatories Very Large Array Sky Survey at 1.4 GHz. We calculate a median spectral index of a = -0.83 between 1.4 GHz and 843 MHz. This version of the catalogue will be released via the World Wide Web with future updates as new mosaics are released.

SUMSS: a wide-field radio imaging survey of the southern sky – II. The source catalogue

We present the results of radio, optical and near-infrared observations of the field of TOC J0233.3+3021, a cluster of milliJansky radio sources from the TexOx Cluster survey. In an observation of this field with the Ryle Telescope (RT) at 15 GHz, we measure a decrement in the cosmic microwave background (CMB) of -675±95 μJy on the RT's≈0.65 kλ baseline. Using optical and infrared imaging with the McDonald 2.7-m Smith Reflector, the Calar Alto 3.5-m telescope and the United Kingdom Infrared Telescope (UKIRT), we identify the host galaxies of five of the radio sources and measure magnitudes of R≈24, J≈20, K≈18.



The cosmic microwave background (CMB) decrement is consistent with the Sunyaev–Zel'dovich (SZ) effect of a massive cluster of galaxies, which if modelled as a spherical King profile of core radius θC=20 arcsec has a central temperature decrement of 900 μK. The magnitudes and colours of the galaxies are consistent with those of old ellipticals at z∼1. We therefore conclude that TOC J0233.3+3021 is a massive, high redshift cluster. These observations add to the growing evidence for a significant population of massive clusters at high redshift, and demonstrate the effectiveness of combining searches for active galactic nuclei (AGN) ‘signposts’ to clusters with the redshift-independence of the SZ effect.

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Detection of a cosmic microwave background decrement towards a cluster of mJy radio sources

We have observed the z=0.78 cluster MS 1137.5+6625 with the Ryle Telescope (RT) at 15 GHz. After subtraction of contaminating radio sources in the field, we find a Sunyaev–Zel'dovich flux decrement of -421±60 μJy on the ≈0.65 kλ baseline of the RT, spatially coincident with the optical and X-ray positions for the cluster core.



For a spherical King-profile cluster model, the best fit to our flux measurement has a core radius θC=20 arcsec, consistent with previous X-ray observations, and a central temperature decrement ΔT=650±92 μK.



Using this model, we calculate that the cluster has a gas mass inside a radius of 2.9×1013 M⊙ for an ΩM=1 universe and 1.6×1013 M⊙ for ΩM=0.3, ΩΛ=0.7. We compare this model with existing measurements of the total mass of the cluster, based on gravitational lensing, and estimate a gas fraction for MS 1137.5+6625 of ≈8 per cent.

Observations of the Sunyaev–Zel'dovich effect in the z=0.78 cluster MS 1137.5+6625

We present the results of radio, optical and near-infrared o bservations of the field of TOC J0233.3+3021, a cluster of milliJansky radiosources from the TexOx Cluster survey. In an observation of this field with the Ryle Telescope (RT) at 15 GHz, we measure a decrement in the cosmic microwave background (CMB) of 675±95µJy on the RT's � 0.65 kbaseline. Using optical and infrared imaging with the McDonald 2.7-m Smith Reflector, Calar Alto 3.5- m telescope and UKIRT, we identify the host galaxies of five of the radiosources and measure magnitudes of R � 24, J � 20, K � 18. The CMB decrement is consistent with the Sunyaev-Zel'dovic h (SZ) effect of a massive cluster of galaxies, which if modelled as a spherical King profile of core radiusC = 20 '' has a central temperature decrement of 900µK. The magnitudes and colours of the galaxies are con- sistent with those of old ellipticals at z � 1. We therefore conclude that TOC J0233.3+3021 is a massive, high redshift cluster. These observations add to the growing evidence for a sig- nificant population of massive clusters at high redshift, an d demonstrate the effectiveness of combining searches for AGN 'signposts' to clusters with the redshift-independence of the SZ effect.

Detection of a CMB decrement towards a cluster of mJy radiosources

Statistical overdensities of radiosources in the Sydney University Molonglo Sky Survey (SUMSS) are used as signposts to identify high-redshift clusters of galaxies. These potential clusters have been observed at 20 and 13 cm at the Australia Telescope Compact Array (ATCA) to obtain better positional accuracy for the sources. A subsample have been imaged in V , R and I at the 2.3-m telescope at Siding Spring and in J and K at the Anglo Australian Telescope (AAT) and the New Technology Telescope (NTT) at La Silla, Chile. The colours obtained from these observations will be used to estimate redshifts for the potential cluster members.

Helen J. Buttery

Papers

SUMSS: a wide-field radio imaging survey of the southern sky – II. The source catalogue

Detection of a cosmic microwave background decrement towards a cluster of mJy radio sources

Observations of the Sunyaev–Zel'dovich effect in the z=0.78 cluster MS 1137.5+6625

Detection of a CMB decrement towards a cluster of mJy radiosources

Searching for Clusters with SUMSS