2001AJ....122..549V


C.D.S. - SIMBAD4 rel 1.7 - 2020.08.10CEST01:49:49

2001AJ....122..549V - Astron. J., 122, 549-564 (2001/August-0)

Composite quasar spectra from the Sloan Digital Sky Survey.

VANDEN BERK D.E., RICHARDS G.T., BAUER A., STRAUSS M.A., SCHNEIDER D.P., HECKMAN T.M., YORK D.G., HALL P.B., FAN X., KNAPP G.R., ANDERSON S.F., ANNIS J., BAHCALL N.A., BERNARDI M., BRIGGS J.W., BRINKMANN J., BRUNNER R., BURLES S., CAREY L., CASTANDER F.J., CONNOLLY A.J., CROCKER J.H., CSABAI I., DOI M., FINKBEINER D., FRIEDMAN S., FRIEMAN J.A., FUKUGITA M., GUNN J.E., HENNESSY G.S., IVEZIC Z., KENT S., KUNSZT P.Z., LAMB D.Q., LEGER R.F., LONG D.C., LOVEDAY J., LUPTON R.H., MEIKSIN A., MERELLI A., MUNN J.A., NEWBERG H.J., NEWCOMB M., NICHOL R.C., OWEN R., PIER J.R., POPE A., ROCKOSI C.M., SCHLEGEL D.J., SIEGMUND W.A., SMEE S., SNIR Y., STOUGHTON C., STUBBS C., SUBBARAO M., SZALAY A.S., SZOKOLY G.P., TREMONTI C., UOMOTO A., WADDELL P., YANNY B. and ZHENG W.

Abstract (from CDS):

We have created a variety of composite quasar spectra using a homogeneous data set of over 2200 spectra from the Sloan Digital Sky Survey (SDSS). The quasar sample spans a redshift range of 0.044≤z≤4.789 and an absolute r' magnitude range of -18.0 to -26.5. The input spectra cover an observed wavelength range of 3800-9200 Å at a resolution of 1800. The median composite covers a rest-wavelength range from 800 to 8555 Å and reaches a peak signal-to-noise ratio of over 300 per 1 Å resolution element in the rest frame. We have identified over 80 emission-line features in the spectrum. Emission-line shifts relative to nominal laboratory wavelengths are seen for many of the ionic species. Peak shifts of the broad permitted and semiforbidden lines are strongly correlated with ionization energy, as previously suggested, but we find that the narrow forbidden lines are also shifted by amounts that are strongly correlated with ionization energy. The magnitude of the forbidden line shifts is ≲100 km.s–1, compared with shifts of up to 550 km.s–1 for some of the permitted and semiforbidden lines. At wavelengths longer than the Lyα emission, the continuum of the geometric mean composite is well fitted by two power laws, with a break at ~5000 Å. The frequency power-law index, αν, is -0.44 from ~1300 to 5000 Å and -2.45 redward of ~5000 Å. The abrupt change in slope can be accounted for partly by host-galaxy contamination at low redshift. Stellar absorption lines, including higher order Balmer lines, seen in the composites suggest that young or intermediate-age stars make a significant contribution to the light of the host galaxies. Most of the spectrum is populated by blended emission lines, especially in the range 1500-3500 Å, which can make the estimation of quasar continua highly uncertain unless large ranges in wavelength are observed. An electronic table of the median quasar template is available.

Abstract Copyright:

Journal keyword(s): Galaxies: Quasars: Emission Lines - Galaxies: Quasars: General

Simbad objects: 8

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Number of rows : 8

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 Mrk 1502 Sy1 00 53 34.9326560879 +12 41 35.927159668   14.41 14.03     ~ 1037 1
2 M 77 GiP 02 42 40.771 -00 00 47.84 9.70 9.61 8.87 10.1 9.9 ~ 4100 2
3 M 42 HII 05 35 17.3 -05 23 28           ~ 3732 0
4 NAME Ori A MoC 05 38 -07.1           ~ 2680 0
5 Mrk 699 Sy1 16 23 45.8804171705 +41 04 56.426364686   17.04 16.61     ~ 114 0
6 NAME Cyg A Sy2 19 59 28.35645829 +40 44 02.0966496   16.22 15.10     ~ 2116 2
7 QSO B2226-3905 QSO 22 29 51.3836374835 -38 50 03.442904142   18.6       ~ 17 1
8 NGC 7469 Sy1 23 03 15.674 +08 52 25.28 12.60 13.00 12.34     ~ 1892 3

    Equat.    Gal    SGal    Ecl

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