An electronic table of the median quasar template is available. 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. 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. The abrupt change in slope can be accounted for partly by host-galaxy contamination at low redshift. 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 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. 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. Emission-line shifts relative to nominal laboratory wavelengths are seen for many of the ionic species. We have identified over 80 emission-line features in the spectrum. 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. The input spectra cover an observed wavelength range of 3800–9200 Å at a resolution of 1800. 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. This can be used to quickly test the QSFit procedures (see below).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 QSFit package comes already with one such file in the data directory. the fiber ID (0323 in the example above).NOTE: this number appears twice in the URL!) the plate ID (0752 in the example above.Verify the resulting object is the one you're interested in and click on FITS (in the middle of the column on the left), and on Download.Īlternativaly you may copy and paste an URL similar to the following:ĭirectly on the web browser. TheseĬlick, on Search, enter search cirteria and click on Go.
#Quasar spectra download
Download the spectra FITS files:Ĭurrently only SDSS DR10 FITS files are supported by QSFit. There is no need to modify your IDL_PATH settings to use QSFit. Best practice is to call compile manually, at the very beginning of the IDL session. The compile procedure and QSFit routines can not be used within the same procedure. Start an IDL session and change to the directory where you downloaded the QSFit files, e.g.: To use QSFit you need IDL (ver >= 8.1) and Gnuplot (ver. If you find QSFit useful please cite the refernce paper: Calderone et al. The whole fitting process is customizable for specific needs, and can be extended to analyze spectra from other data sources. The ultimate purpose of QSFit is to allow astronomers to run standardized recipes to analyze the AGNĭata, in a simple, replicable and shareable way.
#Quasar spectra software
The software provides luminosity estimates for the AGN continuum, the Balmer continuum, both optical and UV ironīlended complex, host galaxy and emission lines, as well as width, velocity offset and equivalent width of 20 emission lines (Halpha, Hbeta, Mgii,, Civ, etc.). QSFit (Quasar Spectral Fitting) is a software package written in IDL to automatically perform the analysis of Active Galactic Nuclei (AGN) optical spectra.