The JHU-SDSS Metal Absorber Catalog
★ If you are interested in the dimensionality reduction technique I developed for spectral modeling, please see the nonnegative matrix factorization page.
★ Catalog Construction

The circum- and inter-galactic medium (IGM & CGM) contains signatures of key processes in galaxy formation such as accretion and outflows, and may account for the majority of baryons in the Universe. Absorption spectroscopy provides us with a unique tool to study the diffuse gas in the Universe. The detection of absorption lines relies on accurate estimation of the intrinsic continuum of background sources and this process has been the main limitation in previous studies. I developed a generic method to automatically estimate the continuum of arbitrary astronomical sources, employing nonnegative matrix factorization (NMF), a variation of the principal component analysis (PCA) technique, and a matched-filter pattern-recognition technique to automatically detect and identify absorption lines.  Applying the algorithms to ~400,000 spectra of bright quasars (supermassive blackholes devouring a large amount of surrounding material) from the SDSS survey, I have compiled ~100,000 Mg II/Fe II (absorption by singly-ionized Mg+ and Fe+) absorption-line systems. The method of catalog construction and the statistics and evolution of the Mg II absorbers are described in Zhu & Ménard 2013a. And here you can find a short visual presentation of how I constructed the catalog.

 

★ Catalog Download

 

The absorber catalogs for DR7, DR9 and DR12 (in FITS format) can be found below (right click the link and choose save link as). DR12 supersedes DR9, which is left only for comparison. Note there are duplicates between DR12 and DR7 due to repeated observations of high-redshift quasars. Some quasars were observed multiple times in DR12 and they are also left in the catalog for consistency (So some entries in DR12 are not unique). If you have any question regarding these data, please email me at guangtun.ben.zhu on Gmail.

 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog (DR7) 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog (DR9) 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog (DR12, supersedes DR9) 

 

The catalogs above are organized based on absorbers and each entry corresponds to one absorber. You can also download the catalogs based on quasars in which each entry corresponds to one quasar:

 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog, Quasar based (DR7) 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog, Quasar based (DR9) 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog, Quasar based (DR12, supersedes DR9) 

 

 

You can also download the quasar catalogs searched for strong absorption-line systems:

 

☆  Quasars seached for Mg II/Fe II Absorbers (DR7) 

☆  Quasars searched for Mg II/Fe II Absorbers (DR9) 

☆  Quasars searched for Mg II/Fe II Absorbers (DR12, supersedes DR9) 

 

The absorption-line systems above are used in the analyses presented in our paper. We are confident with the high purity of these systems and the robustness of the measurements of their properties. However, we required these absorbers to be blueshifted from quasars' Mg II by Δz>0.04 and also redward of C IV by Δz>0.02. We also have expanded catalogs that include absorbers likely associated with quasars (|Δz| < 0.04), those at wavelength blueward of C IV, and those with Fe II detection but no Mg II detections (likely due to bad pixels). These catalogs are not fully-vetted and may contain a small fraction of false positives (mainly C IV absorbers). For statistical studies the false positives should not matter, but if you are interested in individual systems, we encourage you to look at the spectra and use your good judgement.

 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog (DR7, Expanded)

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog (DR9, Expanded) 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog (DR12, Expanded) 

 

The catalogs above are organized based on absorbers and each entry corresponds to one absorber. You can also download the catalogs based on quasars in which each entry corresponds to one quasar:

 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog, Quasar based (DR7, Expanded) 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog, Quasar based (DR9, Expanded) 

☆  The JHU-SDSS Mg II/Fe II Absorber Catalog, Quasar based (DR12, Expanded) 

 

Below is the description of the tags/fields of each entry. For more information, please refer to our paper:Zhu & Ménard 2013a, and feel free to send me a message. Any feedback will be greatly appreciated. 

 

 

 

★ Catalog Description

 

☆  RA: Right ascension, J2000, degrees

☆  DEC: Declination, J2000, degrees

☆  MJD: SDSS Modified Julian Date

☆  PLATE: SDSS Plate ID

☆  FIBER: SDSS Fiber ID

☆  ZQSO: Quasar redshift

☆  NABS: Number of absorbers detected in the quasar spectrum

☆  ZABS or ZABS[10]: Absorber redshift(s)

        -- In the absorber-based catalog, this is the redshift of the absorber. 

        -- In the quasar-based catalog, ZABS[0:NABS-1] gives the redshifts of NABS absorbers detected. 

☆  REW_* or REW_*[10]: Rest equivalent widths of strong lines

        -- In the absorber-based catalog, this is the line REWs of the absorber. 

        -- In the quasar-based catalog, REW_*[0:NABS-1] gives the line REWs of NABS absorbers detected.

☆  ERR_REW_* or ERR_REW_*[10]:

        -- In the absorber-based catalog, this is the errors of the line REWs of the absorber. 

        -- In the quasar-based catalog, REW_*[0:NABS-1] gives the errors of the line REWs of NABS absorbers detected.

 

 

 

★ Some Notes

 

☆  REW are measured with Gaussian fitting.

☆  Absorbers with Δz<0.003 are treated as one absorber.

☆  107 is the pipeline run number. 107 (100+7) means that it is the 7th run of the pipeline.

☆  There are about 10% duplicated systems between DR7 and DR12 because of repeated observations of high-redshift quasars in BOSS (see Paris et al. 2014 for details). They are kept in both catalogs for consistency.

☆  There are about 2000 systems in DR9 that are not in DR12, likely due to reprocessing of the spectra in the new data release. They are kept in the now-outdated DR9 catalog for consistency.

☆  There are also duplicated entries in DR12 due to repeated observations of the same quasar. They are kept in the catalog for consistency.

☆  Please send feedback to guangtun.ben.zhu [AT] gmail [DOT] com. Thank you very much.

★ This work has been funded by the NSF grant AST-1109665 and #HST-HF2-51351

Johns Hopkins University

© 2016 Guangtun Ben Zhu

NASA Hubble Fellowship Program

Quasar Absorbers from SDSS