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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

A probabilistic approach to emission-line galaxy classification

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Author(s):
de Souza, R. S. [1, 2, 3] ; Dantas, M. L. L. [2] ; Costa-Duarte, M. V. [2, 4] ; Feigelson, E. D. [5, 6] ; Killedar, M. [7] ; Lablanche, P. -Y. [8, 9] ; Vilalta, R. [9, 10] ; Krone-Martins, A. [11] ; Beck, R. [12] ; Gieseke, F. [13]
Total Authors: 10
Affiliation:
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[1] MTA Eotvos Univ, EIRSA Lendulet Astrophys Res Grp, H-1117 Budapest - Hungary
[2] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, R do Matao 1226, BR-05508090 Sao Paulo - Brazil
[3] Univ North Carolina Chapel Hill, Dept Phys & Astron, Chapel Hill, NC 27599 - USA
[4] Leiden Univ, Leiden Observ, Niels Bohrweg 2, NL-2333 CA Leiden - Netherlands
[5] Penn State Univ, Dept Astron & Astrostat, Davey Lab 525, University Pk, PA 16802 - USA
[6] Penn State Univ, Ctr Astrostat, Davey Lab 525, University Pk, PA 16802 - USA
[7] Burnet Inst, 85 Commercial Rd, Melbourne, Vic 3004 - Australia
[8] Stellenbosch Univ, ZA-7602 Matieland - South Africa
[9] African Inst Math Sci, 6 Melrose Rd, ZA-7945 Cape Town - South Africa
[10] Univ Houston, Dept Comp Sci, 4800 Calhoun Rd, Houston, TX 77204 - USA
[11] Univ Lisbon, CENTRA SIM, Fac Ciencias, Ed C8, P-1749016 Lisbon - Portugal
[12] Eotvos Lorand Univ, Dept Phys Complex Syst, H-1117 Budapest - Hungary
[13] Radboud Univ Nijmegen, Toernooiveld 212, NL-6525 EC Nijmegen - Netherlands
Total Affiliations: 13
Document type: Journal article
Source: Monthly Notices of the Royal Astronomical Society; v. 472, n. 3, p. 2808-2822, DEC 2017.
Web of Science Citations: 7
Abstract

We invoke a Gaussian mixture model (GMM) to jointly analyse two traditional emission-line classification schemes of galaxy ionization sources: the Baldwin-Phillips-Terlevich (BPT) and W-H alpha versus {[}N-II]/H alpha (WHAN) diagrams, using spectroscopic data from the Sloan Digital Sky Survey Data Release 7 and SEAGal/STARLIGHT data sets. We apply a GMM to empirically define classes of galaxies in a three-dimensional space spanned by the log {[}O (III)]/H beta, log {[}N-II]/H alpha and log EW(H alpha) optical parameters. The best-fitting GMM based on several statistical criteria suggests a solution around four Gaussian components (GCs), which are capable to explain up to 97 per cent of the data variance. Using elements of information theory, we compare each GC to their respective astronomical counterpart. GC1 and GC4 are associated with star-forming galaxies, suggesting the need to define a new starburst subgroup. GC2 is associated with BPT's active galactic nuclei (AGN) class and WHAN's weak AGN class. GC3 is associated with BPT's composite class and WHAN's strong AGN class. Conversely, there is no statistical evidence-based on four GCs-for the existence of a Seyfert/lowionization nuclear emission-line region (LINER) dichotomy in our sample. Notwithstanding, the inclusion of an additional GC5 unravels it. The GC5 appears associated with the LINER and passive galaxies on the BPT and WHAN diagrams, respectively. This indicates that if the Seyfert/LINER dichotomy is there, it does not account significantly to the global data variance and may be overlooked by standard metrics of goodness of fit. Subtleties aside, we demonstrate the potential of our methodology to recover/unravel different objects inside the wilderness of astronomical data sets, without lacking the ability to convey physically interpretable results. The probabilistic classifications from the GMM analysis are publicly available within the COINtoolbox at https://cointoolbox. github. io/GMM\_ Catalogue/. (AU)

FAPESP's process: 16/05254-9 - Investigating galaxy clusters in the photometric redshift space
Grantee:Marcus Vinícius Costa Duarte
Support type: Scholarships abroad - Research Internship - Post-doctor
FAPESP's process: 16/13470-3 - The drivers of star-formation activity in galaxy clusters
Grantee:Laerte Sodré Junior
Support type: Research Grants - Visiting Researcher Grant - International
FAPESP's process: 12/00800-4 - The 3-D universe: astrophysics with large galaxy surveys
Grantee:Laerte Sodré Junior
Support type: Research Projects - Thematic Grants
FAPESP's process: 14/18632-6 - The cosmic web described by superclusters of galaxies
Grantee:Marcus Vinícius Costa Duarte
Support type: Scholarships in Brazil - Post-Doctorate