J/other/PASA/43.47 EMU/GAMA. AGN diagnostics (Prathap+, 2026)
EMU/GAMA: A statistical perspective on active galactic nuclei diagnostics.
Prathap J., Hopkins A.M., Carvajal R., Cowley M., Croom S.M., Farrah D.,
Prandoni I., Shabala S.S., van Loon J.T., Pappalardo C., Pimbblet K.A.,
Ahmed U.T., Bilicki M., Brown M.J.I., Leahy D., Mailvaganam A., Marvil J.R.,
Mukherjee T., Rahman S.F., Vernstrom T., Willingham J., Zafar T.
<Publ. Astron. Soc. Australia PASA, 43, 47 (2026)>
=2026PASA...43...47P 2026PASA...43...47P (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Radio sources
Keywords: galaxies: active - radio continuum: galaxies - methods: statistical
Abstract:
While it is well known that galaxies are composites of many emission
processes, quantifying the various contributions remains challenging.
In this work, we use unsupervised machine learning based clustering
algorithms to evaluate the agreement between the clustering tools and
astrophysical classifications, and hence quantify the fractional
contributions of star formation processes and nuclear black hole
activity to the total galaxy energy budget of radio sources. We
perform clustering on the multiwavelength (optical, infrared (IR), and
radio) active galactic nuclei (AGN) diagnostic spaces, using the data
from the G09 and G23 fields from the Galaxy and Mass Assembly (GAMA)
survey, Evolutionary Map of the Universe (EMU) survey, and
theWide-field Infrared Survey Explorer (WISE).We find that the
statistical clustering recovers ∼90% of the star forming galaxies
(SFGs) and ∼80% of the AGN. We define a new IR-radio AGN diagnostic
scheme that identifies radio AGN from IR SFGs and AGN, corresponding
to the KMeans cluster with approximately 90% reliability. We
demonstrate the superior power of radio AGN selection in higher
dimensions using a three-dimensional space composed of directly
observable parameters (W1-W2 colour, W2 magnitude, and the 1.4GHz
radio flux density). This novel three dimensional diagnostic shows
immense potential in radio AGN selection that is close to 90% reliable
and 90% complete. We also publish a catalogue of radio sources in the
EMU survey with associated probabilities for them to be active in the
optical regime, through which we emphasise the philosophy of
considering a galaxy to be composed of various fractions rather than a
binary classification of SFGs and AGN.
Description:
In this work, we evaluated the performance of different unsupervised
clustering tools in the optical and IR-radio diagnostic spaces, using
an optical-radio sample and an IR-radio sample, respectively. All four
clustering algorithms used, namely KMeans, GMM, FCM, and BIRCH,
performed well in the optical diagnostic spaces, whereas only KMeans
worked well for the IR-radio diagnostic spaces.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 294 4284 AGN probability (or fraction) catalogue
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See also:
J/MNRAS/413/971 : Galaxy And Mass Assembly (GAMA): DR1 (Driver+, 2011)
J/MNRAS/452/2087 : Galaxy And Mass Assembly (GAMA): DR2 (Liske+, 2015)
J/MNRAS/474/3875 : Galaxy And Mass Assembly (GAMA): DR3 (Baldry+, 2018)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- CompId Radio source identifier taken from the
parent G09 and G23 GAMA fields catalogues
(component_id)
25- 39 I15 --- uberID GAMA source id (uberID)
41- 47 I7 --- CATAID GAMA source id (from the GAMA II phase)
(CATAID)
49- 66 F18.14 deg RAdeg Right ascension from EMU (J2000)
(radegcont)
68- 86 F19.15 deg DEdeg Declination from EMU (J2000)
(decdegcont)
88-109 E22.16 arcsec e_RAdeg EMU positional uncertainty in RA (ra_err)
110-132 E23.16 arcsec e_DEdeg EMU positional uncertainty in DE (dec_err)
134-151 F18.14 deg RAcdeg Right ascension of the optical sources
(of the flux-weighted centres, ICRS)
from GAMA (RAcen)
153-172 F20.16 deg DEcdeg Declination of the optical sources
(of the flux-weighted centres, ICRS)
from GAMA (Deccen)
174-184 F11.7 deg RAWdeg CatWISE right ascension (J2000)
(RA_catwise)
186-196 F11.7 deg DEWdeg CatWISE declination (J2000) (DEC_catwise)
198-218 F21.17 mJy Ftot Integrated radio flux density at 943 MHz
(Total_flux)
220-239 F20.18 mJy e_Ftot Uncertainty in the integrated flux density
at 943 MHz (Totalfluxerr)
242-263 E22.20 --- pbAGN-GMM Probability for a source to be AGN as per
the GMM clustering (probagngmm)
265-286 E22.20 --- pbAGN-FCM Probability for a source to be AGN as per
the FCM clustering (probagnfcm)
288 I1 --- KMeansClass [0/1] KMeans cluster label of the source
(KMeans_class)
290 I1 --- GMMClass [0/1] GMM cluster label of the source
(GMM_class)
292 I1 --- FCMClass [0/1] FCM cluster label of the source
(FCM_class)
294 I1 --- BIRCHClass [0/1] BIRCH cluster label of the source
(BIRCH_class)
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Acknowledgements:
Jahang Prathap, jahangprathap12(at)gmail.com
License: CC-BY-4.0 [see https://spdx.org/licenses/]
(End) Patricia Vannier [CDS] 13-Apr-2026