J/A+A/649/A53 Mean galaxy spectra of the 86 classes (Fraix-Burnet+, 2021)
Unsupervised classification of SDSS galaxy spectra.
Fraix-Burnet D., Bouveyron C., Moultaka J.
<Astron. Astrophys. 649, A53 (2021)>
=2021A&A...649A..53F 2021A&A...649A..53F (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Spectral types
Keywords: methods: data analysis - methods: statistical - galaxies: statistics -
galaxies: general - techniques: spectroscopic
Abstract:
Defining templates of galaxy spectra is useful to quickly characterise
new obervations and organise data bases from surveys. These templates
are usually built from a pre-defined classification based on other
criteria.
We present an unsupervised classification of 702248 spectra of
galaxies and quasars with redshifts smaller than 0.25 that were
retrieved from the Sloan Digital Sky Survey (SDSS) database, release 7.
The spectra were first corrected for the redshift, then
wavelet-filtered to reduce the noise, and finally binned to obtain
about 1437 wavelengths per spectrum. Fisher-EM, an unsupervised
clustering discriminative latent mixture model algorithm, was applied
on these corrected spectra, considering the full set as well as
several subsets of 100000 and 300000 spectra.
The optimum number of classes given by a penalised likelihood
criterion is 86 classes, the 37 most populated ones gathering 99% of
the sample. These classes are established from a subset of 302214
spectra. Using several cross-validation techniques we find that this
classification is in agreement with the results obtained on the other
subsets with an average misclassification error of about 15%. The
large number of very small classes tends to increase this error rate.
In this paper, we make a first quick comparison of our classes with
the templates of Kennicutt (1992), Dobos et al (2012), Wang et al
(2018).
This is the first time that an automatic, objective and robust
unsupervised classification is established on such a large amount of
spectra of galaxies. The mean spectra of the classes can be used as
templates for a large majority of galaxies in our Universe.
Description:
The spectra used in this study were retrieved from the SDSS DR7 data
base. They were corrected for redshift, denoised and rebinned as
explained in the paper. They were NOT corrected for extinction. The
full set of processed spectra is available on request. In the table
classk86.dat, we provide the index specObjId of SDSS DR7.
The mean spectra of the 86 classes is provided here in electronic
form, as well as the class for each of the 302248 spectra used for
this classification.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
meansk86.dat 1590 1437 Mean spectra of the 86 classes
classk86.dat 30 302248 Classes K86 of 302248 spectra
tablec1.dat 29 86 *Correspondence between our classes (Fisher-EM)
and those of other atlases
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Note on tablec1.dat: Kennicutt 1992ApJS...79..255K 1992ApJS...79..255K;
Dobos et al. 2012MNRAS.420.1217D 2012MNRAS.420.1217D; Wang et al. 2018MNRAS.474.1873W 2018MNRAS.474.1873W
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See also:
http://skyserver.sdss.org/dr7 : SDSS DR7 Home Page
Byte-by-byte Description of file: meansk86.dat
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Bytes Format Units Label Explanations
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1- 16 F16.11 0.1nm lambda Wavelength (Angstroem)
18- 34 F17.15 --- A8 Mean spectra of class A8
36- 52 F17.15 --- A16 Mean spectra of class A16
54- 70 F17.15 --- A22 Mean spectra of class A22
72- 88 F17.15 --- A35 Mean spectra of class A35
90- 106 F17.15 --- A21 Mean spectra of class A21
108- 124 F17.15 --- A30 Mean spectra of class A30
126- 142 F17.15 --- A23 Mean spectra of class A23
144- 162 F19.16 --- A25 Mean spectra of class A25
164- 180 F17.15 --- A38 Mean spectra of class A38
182- 200 F19.16 --- A4 Mean spectra of class A4
202- 218 F17.15 --- A29 Mean spectra of class A29
220- 236 F17.15 --- A7 Mean spectra of class A7
238- 254 F17.15 --- A43 Mean spectra of class A43
256- 272 F17.15 --- A5 Mean spectra of class A5
274- 290 F17.15 --- A18 Mean spectra of class A18
292- 308 F17.15 --- A11 Mean spectra of class A11
310- 326 F17.15 --- A3 Mean spectra of class A3
328- 344 F17.15 --- A36 Mean spectra of class A36
346- 362 F17.15 --- A50 Mean spectra of class A50
364- 380 F17.15 --- A37 Mean spectra of class A37
382- 398 F17.15 --- A28 Mean spectra of class A28
400- 416 F17.15 --- A6 Mean spectra of class A6
418- 434 F17.15 --- A15 Mean spectra of class A15
436- 452 F17.15 --- A39 Mean spectra of class A39
454- 470 F17.15 --- A2 Mean spectra of class A2
472- 488 F17.15 --- A20 Mean spectra of class A20
490- 506 F17.15 --- A45 Mean spectra of class A45
508- 526 F19.17 --- A46 Mean spectra of class A46
528- 544 F17.15 --- A26 Mean spectra of class A26
546- 562 F17.15 --- A47 Mean spectra of class A47
564- 580 F17.15 --- A32 Mean spectra of class A32
582- 598 F17.15 --- A10 Mean spectra of class A10
600- 616 F17.15 --- A17 Mean spectra of class A17
618- 635 F18.15 --- A48 Mean spectra of class A48
637- 653 F17.15 --- A13 Mean spectra of class A13
655- 672 F18.16 --- A44 Mean spectra of class A44
674- 690 F17.15 --- A9 Mean spectra of class A9
692- 708 F17.15 --- A49 Mean spectra of class A49
710- 727 F18.15 --- A40 Mean spectra of class A40
729- 745 F17.15 --- A34 Mean spectra of class A34
747- 763 F17.15 --- A19 Mean spectra of class A19
765- 781 F17.15 --- A31 Mean spectra of class A31
783- 799 F17.15 --- A33 Mean spectra of class A33
801- 817 F17.15 --- A41 Mean spectra of class A41
819- 835 F17.15 --- A27 Mean spectra of class A27
837- 853 F17.15 --- A24 Mean spectra of class A24
855- 871 F17.15 --- A12 Mean spectra of class A12
873- 889 F17.15 --- A42 Mean spectra of class A42
891- 907 F17.15 --- A1 Mean spectra of class A1
909- 925 F17.15 --- A14 Mean spectra of class A14
927- 944 F18.15 --- B12 Mean spectra of class B12
946- 963 F18.16 --- B20 Mean spectra of class B20
965- 981 F17.15 --- B7 Mean spectra of class B7
983- 999 F17.15 --- B19 Mean spectra of class B19
1001-1017 F17.15 --- B14 Mean spectra of class B14
1019-1036 F18.15 --- B6 Mean spectra of class B6
1038-1055 F18.15 --- B24 Mean spectra of class B24
1057-1073 F17.15 --- B5 Mean spectra of class B5
1075-1093 F19.17 --- B21 Mean spectra of class B21
1095-1111 F17.15 --- B1 Mean spectra of class B1
1113-1129 F17.15 --- B16 Mean spectra of class B16
1131-1147 F17.15 --- B2 Mean spectra of class B2
1149-1165 F17.15 --- B13 Mean spectra of class B13
1167-1183 F17.15 --- B17 Mean spectra of class B17
1185-1201 F17.15 --- B8 Mean spectra of class B8
1203-1222 F20.17 --- B23 Mean spectra of class B23
1224-1240 F17.15 --- B15 Mean spectra of class B15
1242-1258 F17.15 --- B3 Mean spectra of class B3
1260-1276 F17.15 --- B4 Mean spectra of class B4
1278-1295 F18.16 --- B25 Mean spectra of class B25
1297-1313 F17.15 --- B10 Mean spectra of class B10
1315-1331 F17.15 --- B9 Mean spectra of class B9
1333-1349 F17.15 --- B22 Mean spectra of class B22
1351-1367 F17.15 --- B18 Mean spectra of class B18
1369-1385 F17.15 --- B11 Mean spectra of class B11
1387-1403 F17.15 --- C9 Mean spectra of class C9
1405-1422 F18.15 --- C7 Mean spectra of class C7
1424-1441 F18.15 --- C10 Mean spectra of class C10
1443-1460 F18.15 --- C1 Mean spectra of class C1
1462-1479 F18.15 --- C3 Mean spectra of class C3
1481-1498 F18.15 --- C6 Mean spectra of class C6
1500-1516 F17.15 --- C5 Mean spectra of class C5
1518-1534 F17.15 --- C8 Mean spectra of class C8
1536-1553 F18.15 --- C2 Mean spectra of class C2
1555-1571 F17.15 --- C4 Mean spectra of class C4
1573-1590 F18.15 --- D Mean spectra of class D
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Byte-by-byte Description of file: classk86.dat
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Bytes Format Units Label Explanations
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1- 18 I18 --- specObjID The SDSS index of the spectrum
20- 30 A11 --- FEMK86class The class of each spectrum (1)
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Note (1): Class "Disregarded" indicates the 34 weird spectra that were not
used in the classification.
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Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Class Fisher-EM class (this paper) (1)
5- 9 A5 --- K92 Kennicutt (1992ApJS...79..255K 1992ApJS...79..255K, Cat. VII/141)
class
11- 16 A6 --- D12 Dobos et al. (2012MNRAS.420.1217D 2012MNRAS.420.1217D) class (2)
18- 29 A12 --- W18 Wang et al. (2018MNRAS.474.1873W 2018MNRAS.474.1873W,
Cat. J/MNRAS/474/1873) class
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Note (1): Our classes are ordered according to their number of spectra.
Note (2): Dobos et al. (2012MNRAS.420.1217D 2012MNRAS.420.1217D) define the nomenclature as:
p = passive
l = LINER
s = Seyfert
h = Hα
hh = AGN+HII
t = all
BG = all blue galaxies
GG = all green galaxies
RG = all red galaxies
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Acknowledgements:
Didier Fraix-Burnet, didier.fraix-burnet(at)univ-grenoble-alpes.fr
(End) D. Fraix-Burnet [IPAG/CNRS/UGA, France], P. Vannier [CDS] 19-Feb-2021