THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: AN INVESTIGATION OF BIASES IN C iv EMISSION LINE PROPERTIES
ABSTRACT We investigate the dependence on data quality of quasar properties measured from the C iv emission line region at high redshifts. Our measurements come from 32 epochs of Sloan Digital Sky Survey Reverberation Mapping Project spectroscopic observations of 482 quasars. We compare the differen...
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| creator | Denney, K. D. Horne, Keith Shen, Yue Brandt, W. N. Ho, Luis C. Peterson, B. M. Richards, Gordon T. Trump, J. R. Ge, J. |
| description | ABSTRACT We investigate the dependence on data quality of quasar properties measured from the C iv emission line region at high redshifts. Our measurements come from 32 epochs of Sloan Digital Sky Survey Reverberation Mapping Project spectroscopic observations of 482 quasars. We compare the differences between measurements made from the single-epoch (SE) and coadded spectra, focusing on the C iv λ1549 emission line because of its importance for studies of high-redshift quasar demographics and physical properties, including black hole masses. In addition to statistical errors increasing (by factors of ∼2-4), we find increasing systematic offsets with decreasing signal-to-noise ratio (S/N). The systematic difference (measurement uncertainty) in our lowest-S/N ( |
| doi_str_mv | 10.3847/0067-0049/224/2/14 |
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D. ; Horne, Keith ; Shen, Yue ; Brandt, W. N. ; Ho, Luis C. ; Peterson, B. M. ; Richards, Gordon T. ; Trump, J. R. ; Ge, J.</creator><creatorcontrib>Denney, K. D. ; Horne, Keith ; Shen, Yue ; Brandt, W. N. ; Ho, Luis C. ; Peterson, B. M. ; Richards, Gordon T. ; Trump, J. R. ; Ge, J.</creatorcontrib><description>ABSTRACT We investigate the dependence on data quality of quasar properties measured from the C iv emission line region at high redshifts. Our measurements come from 32 epochs of Sloan Digital Sky Survey Reverberation Mapping Project spectroscopic observations of 482 quasars. We compare the differences between measurements made from the single-epoch (SE) and coadded spectra, focusing on the C iv λ1549 emission line because of its importance for studies of high-redshift quasar demographics and physical properties, including black hole masses. In addition to statistical errors increasing (by factors of ∼2-4), we find increasing systematic offsets with decreasing signal-to-noise ratio (S/N). The systematic difference (measurement uncertainty) in our lowest-S/N (<5) subsample between the SE and coadded spectrum (i) C iv equivalent width is 17 Å (31 Å), (ii) centroid wavelength is <1 Å (2 Å), and fractional velocity widths, , characterized by (iii) the line dispersion, l, is 0.104 (0.12), and (iv) the mean absolute deviation (MAD) is 0.072 (0.11). These remain smaller than the 1 measurement uncertainties for all subsamples considered. The MAD is found to be the most robust line-width characterization. Offsets in the C iv FWHM velocity width and the C iv profile characterized by FWHM/ l are only smaller than the statistical uncertainties when S/N > 10, although offsets in lower-S/N spectra exceed the statistical uncertainties by only a factor of ∼1.5 and may depend on the type of functional fit to the line. Characterizing the C iv line profile by the kurtosis is the least robust property investigated, as the median systematic coadded-SE measurement differences are larger than the statistical uncertainties for all S/N subsamples.</description><identifier>ISSN: 0067-0049</identifier><identifier>EISSN: 1538-4365</identifier><identifier>DOI: 10.3847/0067-0049/224/2/14</identifier><language>eng</language><publisher>United States: The American Astronomical Society</publisher><subject>ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ; BLACK HOLES ; Emission analysis ; Emission spectroscopy ; GALAXIES ; galaxies: active ; galaxies: nuclei ; LINE WIDTHS ; MASS ; Offsets ; PHYSICAL PROPERTIES ; QUASARS ; quasars: emission lines ; quasars: general ; quasars: supermassive black holes ; RED SHIFT ; Robustness ; SIGNAL-TO-NOISE RATIO ; Sky surveys (astronomy) ; SPECTRA ; Spectral lines ; STATISTICS ; TELESCOPES ; Uncertainty ; WAVELENGTHS</subject><ispartof>The Astrophysical journal. 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D.</creatorcontrib><creatorcontrib>Horne, Keith</creatorcontrib><creatorcontrib>Shen, Yue</creatorcontrib><creatorcontrib>Brandt, W. N.</creatorcontrib><creatorcontrib>Ho, Luis C.</creatorcontrib><creatorcontrib>Peterson, B. M.</creatorcontrib><creatorcontrib>Richards, Gordon T.</creatorcontrib><creatorcontrib>Trump, J. R.</creatorcontrib><creatorcontrib>Ge, J.</creatorcontrib><title>THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: AN INVESTIGATION OF BIASES IN C iv EMISSION LINE PROPERTIES</title><title>The Astrophysical journal. Supplement series</title><addtitle>APJS</addtitle><addtitle>Astrophys. J. Suppl</addtitle><description>ABSTRACT We investigate the dependence on data quality of quasar properties measured from the C iv emission line region at high redshifts. Our measurements come from 32 epochs of Sloan Digital Sky Survey Reverberation Mapping Project spectroscopic observations of 482 quasars. We compare the differences between measurements made from the single-epoch (SE) and coadded spectra, focusing on the C iv λ1549 emission line because of its importance for studies of high-redshift quasar demographics and physical properties, including black hole masses. In addition to statistical errors increasing (by factors of ∼2-4), we find increasing systematic offsets with decreasing signal-to-noise ratio (S/N). The systematic difference (measurement uncertainty) in our lowest-S/N (<5) subsample between the SE and coadded spectrum (i) C iv equivalent width is 17 Å (31 Å), (ii) centroid wavelength is <1 Å (2 Å), and fractional velocity widths, , characterized by (iii) the line dispersion, l, is 0.104 (0.12), and (iv) the mean absolute deviation (MAD) is 0.072 (0.11). These remain smaller than the 1 measurement uncertainties for all subsamples considered. The MAD is found to be the most robust line-width characterization. Offsets in the C iv FWHM velocity width and the C iv profile characterized by FWHM/ l are only smaller than the statistical uncertainties when S/N > 10, although offsets in lower-S/N spectra exceed the statistical uncertainties by only a factor of ∼1.5 and may depend on the type of functional fit to the line. 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D.</creator><creator>Horne, Keith</creator><creator>Shen, Yue</creator><creator>Brandt, W. N.</creator><creator>Ho, Luis C.</creator><creator>Peterson, B. M.</creator><creator>Richards, Gordon T.</creator><creator>Trump, J. R.</creator><creator>Ge, J.</creator><general>The American Astronomical Society</general><scope>AAYXX</scope><scope>CITATION</scope><scope>7TG</scope><scope>KL.</scope><scope>8FD</scope><scope>H8D</scope><scope>L7M</scope><scope>OTOTI</scope><orcidid>https://orcid.org/0000-0002-0167-2453</orcidid><orcidid>https://orcid.org/0000-0001-6947-5846</orcidid><orcidid>https://orcid.org/0000-0002-1410-0470</orcidid></search><sort><creationdate>20160601</creationdate><title>THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: AN INVESTIGATION OF BIASES IN C iv EMISSION LINE PROPERTIES</title><author>Denney, K. D. ; Horne, Keith ; Shen, Yue ; Brandt, W. N. ; Ho, Luis C. ; Peterson, B. M. ; Richards, Gordon T. ; Trump, J. 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D.</creatorcontrib><creatorcontrib>Horne, Keith</creatorcontrib><creatorcontrib>Shen, Yue</creatorcontrib><creatorcontrib>Brandt, W. N.</creatorcontrib><creatorcontrib>Ho, Luis C.</creatorcontrib><creatorcontrib>Peterson, B. M.</creatorcontrib><creatorcontrib>Richards, Gordon T.</creatorcontrib><creatorcontrib>Trump, J. R.</creatorcontrib><creatorcontrib>Ge, J.</creatorcontrib><collection>CrossRef</collection><collection>Meteorological & Geoastrophysical Abstracts</collection><collection>Meteorological & Geoastrophysical Abstracts - Academic</collection><collection>Technology Research Database</collection><collection>Aerospace Database</collection><collection>Advanced Technologies Database with Aerospace</collection><collection>OSTI.GOV</collection><jtitle>The Astrophysical journal. Supplement series</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext_linktorsrc</fulltext></delivery><addata><au>Denney, K. D.</au><au>Horne, Keith</au><au>Shen, Yue</au><au>Brandt, W. N.</au><au>Ho, Luis C.</au><au>Peterson, B. M.</au><au>Richards, Gordon T.</au><au>Trump, J. R.</au><au>Ge, J.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: AN INVESTIGATION OF BIASES IN C iv EMISSION LINE PROPERTIES</atitle><jtitle>The Astrophysical journal. Supplement series</jtitle><stitle>APJS</stitle><addtitle>Astrophys. J. Suppl</addtitle><date>2016-06-01</date><risdate>2016</risdate><volume>224</volume><issue>2</issue><spage>14</spage><epage>14</epage><pages>14-14</pages><issn>0067-0049</issn><eissn>1538-4365</eissn><abstract>ABSTRACT We investigate the dependence on data quality of quasar properties measured from the C iv emission line region at high redshifts. Our measurements come from 32 epochs of Sloan Digital Sky Survey Reverberation Mapping Project spectroscopic observations of 482 quasars. We compare the differences between measurements made from the single-epoch (SE) and coadded spectra, focusing on the C iv λ1549 emission line because of its importance for studies of high-redshift quasar demographics and physical properties, including black hole masses. In addition to statistical errors increasing (by factors of ∼2-4), we find increasing systematic offsets with decreasing signal-to-noise ratio (S/N). The systematic difference (measurement uncertainty) in our lowest-S/N (<5) subsample between the SE and coadded spectrum (i) C iv equivalent width is 17 Å (31 Å), (ii) centroid wavelength is <1 Å (2 Å), and fractional velocity widths, , characterized by (iii) the line dispersion, l, is 0.104 (0.12), and (iv) the mean absolute deviation (MAD) is 0.072 (0.11). These remain smaller than the 1 measurement uncertainties for all subsamples considered. The MAD is found to be the most robust line-width characterization. Offsets in the C iv FWHM velocity width and the C iv profile characterized by FWHM/ l are only smaller than the statistical uncertainties when S/N > 10, although offsets in lower-S/N spectra exceed the statistical uncertainties by only a factor of ∼1.5 and may depend on the type of functional fit to the line. Characterizing the C iv line profile by the kurtosis is the least robust property investigated, as the median systematic coadded-SE measurement differences are larger than the statistical uncertainties for all S/N subsamples.</abstract><cop>United States</cop><pub>The American Astronomical Society</pub><doi>10.3847/0067-0049/224/2/14</doi><tpages>15</tpages><orcidid>https://orcid.org/0000-0002-0167-2453</orcidid><orcidid>https://orcid.org/0000-0001-6947-5846</orcidid><orcidid>https://orcid.org/0000-0002-1410-0470</orcidid></addata></record> |
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| subjects | ASTROPHYSICS, COSMOLOGY AND ASTRONOMY BLACK HOLES Emission analysis Emission spectroscopy GALAXIES galaxies: active galaxies: nuclei LINE WIDTHS MASS Offsets PHYSICAL PROPERTIES QUASARS quasars: emission lines quasars: general quasars: supermassive black holes RED SHIFT Robustness SIGNAL-TO-NOISE RATIO Sky surveys (astronomy) SPECTRA Spectral lines STATISTICS TELESCOPES Uncertainty WAVELENGTHS |
| title | THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: AN INVESTIGATION OF BIASES IN C iv EMISSION LINE PROPERTIES |
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