J/MNRAS/537/1459 Activity diagnostic via PCA of visible spectra (Tous+, 2025)
Fully comprehensive diagnostic of galaxy activity using principal components of
visible spectra: implementation on nearby S0s.
Tous J.L., Solanes J.M., Perea J.D.
<Mon. Not. R. Astron. Soc. 537, 1459-1469 (2025)>
=2025MNRAS.537.1459T 2025MNRAS.537.1459T (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, optical ; Galaxies, spectra ; Morphology
Keywords: galaxies: active - galaxies: elliptical and lenticular, cD -
galaxies: Seyfert - galaxies: star formation - galaxies: statistics
Abstract:
We introduce a novel galaxy classification methodology based on the
visible spectra of a sample of over 68000 nearby (z≤0.1) Sloan
Digital Sky Survey lenticular (S0) galaxies. Unlike traditional
diagnostic diagrams, which rely on a limited set of emission lines and
class dividers to identify ionizing sources, our approach provides a
comprehensive framework for characterizing galaxies regardless of
their activity level. By projecting galaxies into the 2D latent space
defined by the first three principal components (PCs) of their entire
visible spectra, our method remains robust even when data from
individual emission lines are missing. We employ Gaussian kernel
density estimates of the classical Baldwin-Phillips-Terlevich (BPT)
activity classes in the new classification subspace, adjusted
according to their relative abundance in our S0 sample, to generate
probability maps for star-forming, Seyfert, composite, and LINER
galaxies. These maps closely mirror the canonical distribution of BPT
classes shown by the entire galaxy population, demonstrating that our
PC-based taxonomy effectively predicts the dominant ionizing
mechanisms through a probabilistic approach that provides a realistic
reflection of galaxy activity and allows for refined class membership.
Our analysis further reveals that flux- limited BPT-like diagrams are
inherently biased against composite and star- forming galaxies due to
their weaker [OIII] emission. Besides, it suggests that although most
low-activity galaxies excluded from these diagnostics exhibit visual
spectra with LINER-like characteristics, their remaining activity is
likely driven by mechanisms unrelated to either star formation or
supermassive black hole accretion.
Description:
DPS-PC3 coordinates, spectral class and probability of BPT type for
SDSS S0 galaxies with z ≤ 0.1. The coordinates were obtained in Tous
et al. (2020MNRAS.495.4135T 2020MNRAS.495.4135T) and Jimenez-Palau et al.
(2022MNRAS.515.3956J 2022MNRAS.515.3956J, Cat. J/MNRAS/515/3956) from the visible spectra
of the S0 galaxies.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 95 68042 DPS-PC3 coordinates, spectral class, probability
of BPT type, and activity class inferred from
the traditional BPT-NII diagram
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See also:
J/MNRAS/515/3956 : PCA characterization of activity in S0s
(Jimenez-Palau+, 2022)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- objID SDSS object identifier
21- 29 E9.1 --- PC3 Projection of spectrum onto 3rth component
31- 39 E9.1 --- DeltaPS Distance from the passive sequence
41- 42 A2 --- SpClass [AC PS TR] Spectral class from Tous et al.
(2020MNRAS.495.4135T 2020MNRAS.495.4135T) (1)
44- 52 E9.1 --- Pstarforming Probability of being star forming (2)
54- 62 E9.1 --- Pcomposite Probability of being composite (2)
64- 72 E9.1 --- PLINER Probability of being LINER (2)
74- 82 E9.1 --- PSeyfert Probability of being Seyfert (2)
84- 95 A12 --- BPTClass Activity class from BPT-NII diagram
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Note (1): Spectral class as follows:
AC = active cloud
PS = passive sequence
TR = transition region
Note (2): Probabilities were derived from eq. (2) assuming P(BPT0)=0.
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Acknowledgements:
J.L. Tous, j.l.tous-mayol(at)soton.ac.uk
(End) Patricia Vannier [CDS] 24-Jan-2025