J/MNRAS/474/1873 Classification of LAMOST DR4 galaxies (Wang+, 2018)
Spectral classification and composites of galaxies in LAMOST DR4.
Wang L.-L., Luo A.-L., Shen S.-Y., Hou W., Kong X., Song Y.-H.,
Zhang J.-N., Wu H., Cao Z.-H., Hou Y.-H., Wang Y.-F., Zhang Y., Zhao Y.-H.
<Mon. Not. R. Astron. Soc., 474, 1873-1885 (2018)>
=2018MNRAS.474.1873W 2018MNRAS.474.1873W (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galaxy catalogs ; Photometry, SDSS ; Spectroscopy
Keywords: methods: data analysis - techniques: spectroscopic - catalogues -
galaxies: statistics
Abstract:
We study the classification and composite spectra of galaxies in the
fourth data release (DR4) of the Large Sky Area Multi-Object Fibre
Spectroscopic Telescope (LAMOST). We select 40182 spectra of
galaxies from LAMOST DR4, which have photometric information but no
spectroscopic observations in the Sloan Digital Sky Survey (SDSS).
These newly observed spectra are recalibrated and classified into six
classes - passive, Hα-weak, star-forming, composite, LINER and
Seyfert - using the line intensity (Hβ, [OIII] 5007, Hα
and [NII] 6585). We also study the correlation between spectral class
and morphological type through three parameters: concentration index,
(u-r) colour and D4000n index. We calculate composite spectra of
high signal-to-noise ratio (S/N) for six spectral classes and, using
these composites, we pick out some features that can differentiate the
classes effectively, including Hβ, Fe5015, HγA, HK and the
Mg2 band. In addition, we compare our composite spectra with the SDSS
ones and analyse their differences. A galaxy catalogue of 40182 newly
observed spectra (36601 targets) and the composite spectra of the six
classes are available online
(http://sciwiki.lamost.org/downloads/wll).
Description:
We present a catalogue of galaxies for our Main sample, which have
photometric information without spectroscopic observations in SDSS.
One aim of our work is to provide a catalogue for the newly observed
galaxies in LAMOST, which have no spectral observations in SDSS. We
give the fluxes of nebular emission lines and the classification
information in this catalogue. There are 40182 entries (36601
targets) in the catalogue.
There are five kinds of information: basic information retrieved from
the LAMOST catalogue; Petrosian magnitudes cross-matched with the
photometric catalogue of SDSS; three parameters of correlation with
morphological type; the fluxes of lines we computed in Section 3; and
the spectral class using our classification scheme. Note that the
morphological types are not given directly; instead, three parameters
related to the morphological type are provided: concentration index,
(u-r) colour and D4000n index.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
catalog.dat 207 40182 Galaxy catalogue with classification and
related information for our Main sample
--------------------------------------------------------------------------------
See also:
V/153 : LAMOST DR4 catalogs (Luo+, 2018)
Byte-by-byte Description of file: catalog.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- LAMOST LAMOST name (JHHMMSS.ss+DDMMSS.s)
21 A1 --- n_LAMOST [ab] Note (1)
23- 32 F10.6 deg RAdeg Right ascension (J2000)
34- 43 F10.6 deg DEdeg Declination (J2000)
45- 52 F8.6 --- z Redshift
54- 63 F10.6 --- SNRr ?=999 Signal-to-noise in r band
from LAMOST catalog
65- 76 F12.6 mag umag ?=-9999 SDSS Petrosian u magnitude
78- 89 F12.6 mag gmag ?=-9999 SDSS Petrosian g magnitude
91-102 F12.6 mag rmag ?=-9999 SDSS Petrosian r magnitude
104-115 F12.6 mag imag ?=-9999 SDSS Petrosian i magnitude
117-128 F12.6 mag zmag ?=-9999 SDSS Petrosian z magnitude
130-134 F5.2 --- C Concentration index (2)
136-145 F10.6 mag u-r SDSS u-r colour index
147-158 F12.6 --- D4000n 4000Å break (3)
160-169 F10.4 10-19W/m2/nm FHb ?=- Hβ line flux
(in 10-17erg/cm2/s/Å unit)
171-181 F11.4 10-19W/m2/nm FOIII ?=- [OIII] line flux
(in 10-17erg/cm2/s/Å unit)
183-193 F11.4 10-19W/m2/nm FHa ?=- Hα line flux
(in 10-17erg/cm2/s/Å unit)
195-205 F11.4 10-19W/m2/nm FNII ?=- [NII] line flux
(in 10-17erg/cm2/s/Å unit)
207 I1 --- SClass [0/5]?=- Spectral class (4)
--------------------------------------------------------------------------------
Note (1): Note as follows:
a = upper right corner of the designation if the spectra are from a subsample
in the Northern Galactic Cap, which includes 2859 spectra complementary
to the SDSS main galaxy sample in the study of galaxy pairs
b = spectra targeted from LCSSPA at the Southern Galactic Cap,
including 4493 spectra
Note (2): concentration index computed using petroR90, petroR50 in the r-band
cross-matched photometric catalogue of SDSS.
Note (3): computed using the narrow definition D4000n introduced by
Balogh et al. (1999ApJ...527...54B 1999ApJ...527...54B).
Note (4): spectral class using our classification scheme as follows:
0 = passive
1 = star-forming
2 = composite
3 = LINER
4 = Seyfert
5 = Hα-weak
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 17-Feb-2021