We present the results of a programme to search and identify the nature of unusual sources within the All-sky Wide-field Infrared Survey Explorer (WISE) that is based on a machine-learning algorithm for anomaly detection, namely one-class support vector machines (OCSVM). Designed to detect sources deviating from a training set composed of known classes, this algorithm was used to create a model for the expected data based on WISE objects with spectroscopic identifications in the Sloan Digital Sky Survey (SDSS). Subsequently, it marked as anomalous those sources whose WISE photometry was shown to be inconsistent with this model. We report the results from optical and near-infrared spectroscopy follow-up observations of a subset of 36 bright ($g_{AB}$<19.5) objects marked as 'anomalous' by the OCSVM code to verify its performance. Among the observed objects, we identified three main types of sources: i) low redshift (z~0.03-0.15) galaxies containing large amounts of hot dust (53%), including three Wolf-Rayet galaxies; ii) broad-line quasi-stellar objects (QSOs) (33%) including low-ionisation broad absorption line (LoBAL) quasars and a rare QSO with strong and narrow ultraviolet iron emission; iii) Galactic objects in dusty phases of their evolution (3%). The nature of four of these objects (11%) remains undetermined due to low signal-to-noise or featureless spectra. The current data show that the algorithm works well at detecting rare but not necessarily unknown objects among the brightest candidates. They mostly represent peculiar sub-types of otherwise well-known sources.

/pdf/spectroscopic-observations-of-the-machine-learning-selected-1blt5nmivp.pdf

Spectroscopic observations of the machine-learning selected anomaly catalogue from the AllWISE Sky Survey

We use the new release of the AKARI Far-Infrared all sky Survey matched with the NVSS radio database to investigate the local ($z<0.25$) far infrared-radio correlation (FIRC) of different types of extragalactic sources. To obtain the redshift information for the AKARI FIS sources we crossmatch the catalogue with the SDSS DR8. This also allows us to use emission line properties to divide sources into four categories: i) star-forming galaxies (SFGs), ii) composite galaxies (displaying both star-formation and active nucleus components), iii) Seyfert galaxies, and iv) low-ionization nuclear emission-line region (LINER) galaxies. 
We find that the Seyfert galaxies have the lowest FIR/radio flux ratios and display excess radio emission when compared to the SFGs. We conclude that FIRC can be used to separate SFGs and AGNs only for the most radio-loud objects.

Radio-infrared correlation for local dusty galaxies and dusty AGNs from the AKARI All-Sky Survey

Radio-Infrared Correlation for Local Dusty Galaxies and Dusty AGNs from the AKARI All Sky Survey

We present the results of a programme to search and identify the nature of unusual sources within the All-sky Wide-field Infrared Survey Explorer (WISE) that is based on a machine-learning algorithm for anomaly detection, namely one-class support vector machines (OCSVM). Designed to detect sources deviating from a training set composed of known classes, this algorithm was used to create a model for the expected data based on WISE objects with spectroscopic identifications in the Sloan Digital Sky Survey. Subsequently, it marked as anomalous those sources whose WISE photometry was shown to be inconsistent with this model. We report the results from optical and near-infrared spectroscopy follow-up observations of a subset of 36 bright (g AB  ∼ 0.03 − 0.15) galaxies containing large amounts of hot dust (53%), including three Wolf-Rayet galaxies; (ii) broad-line quasi-stellar objects (QSOs) (33%) including low-ionisation broad absorption line (LoBAL) quasars and a rare QSO with strong and narrow ultraviolet iron emission; (iii) Galactic objects in dusty phases of their evolution (3%). The nature of four of these objects (11%) remains undetermined due to low signal-to-noise or featureless spectra. The current data show that the algorithm works well at detecting rare but not necessarily unknown objects among the brightest candidates. They mostly represent peculiar sub-types of otherwise well-known sources. To search for even more unusual sources, a more complete and balanced training set should be created after including these rare sub-species of otherwise abundant source classes, such as LoBALs. Such an iterative approach will ideally bring us closer to improving the strategy design for the detection of rarer sources contained within the vast data store of the AllWISE survey.

/pdf/spectroscopic-observations-of-the-machine-learning-selected-9u395eu50m.pdf

Radio emission from dusty galaxies observed by AKARI

It is a long known fact that there exists a tight correlation between far-infrared and radioemission both for galaxies hosting active galactic nuclei and for star forming galaxies. We probe theradio - infrared correlation for a sample of extragalactic sources constructed by the cross-correlationof the AKARI/IRC All-Sky Survey Point Source Catalogue, the AKARI/FIS All-Sky Survey BrightSource Catalogue, and the NRAO VLA Sky Survey. Additionally, all objects of our sample wereidentiﬁed as galaxies in NED and SIMBAD databases, and a part of them is known to host activegalactic nuclei (AGNs). After remeasuring all the ﬂuxes, in order to avoid small aperture eﬀects,we compare the ratio of radio to infrared emission from diﬀerent types of extragalactic sources,and discuss the FIR/radio correlation as seen by AKARI and make a comparison to the previousresults obtained thanks to IRAS. Key words: infrared; radio; galaxies; FRC1. INTRODUCTIONThe radio and far-infrared (FIR) luminosities of galax-ies are approximately linearly correlated (e.g., Helou etal., 1985; Mauch & Sadler, 2007; Mori´c et al., 2010).The far-infrared – radio correlation (FRC) is one ofthe most universal empirical correlations known amongthe global parameters of observed galaxies. It spansa wide range of galaxy types and seems to be validboth for the local and the distant universe. PresentlyFRC is believed to be driven mostly by star formation.However, the infrared and radio emission mechanismsin star forming galaxies involve very diﬀerent physicalprocesses and timescales. Moreover, the correlation isalso observed for AGN-hosting galaxies. Hence, it isnot yet established if the FRC is related only to starformation activity, or maybe some other processes areinvolved.This paper presents some preliminary results ofstudies of the FRC for nearby galaxies (

/pdf/radio-emission-from-akari-galaxies-20ognbgt7e.pdf

W. Jurusik

Papers

Radio emission from dusty galaxies observed by AKARI

Radio emission from AKARI galaxies