J/ApJ/862/22 CIV broad abs. line SDSS QSO obs. with Gemini (Rogerson+, 2018) ================================================================================ Emergence and variability of broad absorption line quasar outflows. Rogerson J.A., Hall P.B., Ahmed N.S., Hidalgo P.R., Brandt W.N., Ak N.F. =2018ApJ...862...22R ================================================================================ ADC_Keywords: QSOs; Spectra, optical; Redshifts Keywords: galaxies: active ; quasars: absorption lines Abstract: We isolate a set of quasars that exhibit emergent CIV broad absorption lines (BALs) in their spectra by comparing spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 and the SDSS/BOSS Data Releases 9 and 10. After visually defining a set of emergent BALs, follow-up observations were obtained with the Gemini Observatory for 105 quasars. We find an emergence rate consistent with the previously reported disappearance rate of BAL quasars given the relative numbers of non-BAL and BAL quasars in the SDSS. We find that candidate newly emerged BALs are preferentially drawn from among BALs with smaller balnicity indices, shallower depths, larger velocities, and smaller widths. Within two rest-frame years (average) after a BAL has emerged, we find it equally likely to continue increasing in equivalent width in an observation 6 months later (average) as it is to start decreasing. From the time separations between our observations, we conclude that the coherence timescale of BALs is less than 100 rest-frame days. We observe coordinated variability among pairs of troughs in the same quasar, likely due to clouds at different velocities responding to the same changes in ionizing flux, and the coordination is stronger if the velocity separation between the two troughs is smaller. We speculate that the latter effect may be due to clouds having on average lower densities at higher velocities owing to mass conservation in an accelerating flow, causing the absorbing gas in those clouds to respond on different timescales to the same ionizing flux variations. Description: The SDSS used a dedicated 2.5m f/5 Ritchey-Chretien altitude-azimuth telescope located at Apache Point Observatory in New Mexico, USA. The telescope was outfitted with a photometric camera and a multi-object, fiber-fed spectrograph with a wavelength coverage of 3800-9200{AA} and a resolving power from 1500 to 3000. We leveraged the multi-epoch nature of the DR7, DR9, and DR10 catalogs to search for a set of quasars that had been spectroscopically observed at least twice over all three data releases. We obtained data on 105 targets from the candidate emergence sample using the twin Gemini telescopes. We used the Gemini Multi-object Spectrograph (GMOS) (one on each telescope), outfitted with a 1.0" wide long slit to observe individually each target in our sample. Our Gemini follow-up of the 105 targets was spread over three observing semesters: 2013A, 2013B, and 2014A. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table3.dat 104 105 *List of the observations made for each of the 105 quasars in this work table4.dat 60 105 The rest-frame time between successive observations of a given quasar -------------------------------------------------------------------------------- Note on table3.dat: the spectra are only available on demand to the author. -------------------------------------------------------------------------------- See also: II/183 : UBVRI Photometric Standards (Landolt 1992) II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009) VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010) V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012) VII/270 : SDSS quasar catalog: tenth data release (Paris+, 2014) VII/279 : SDSS quasar catalog: twelfth data release (Paris+, 2017) J/ApJ/641/78 : CIV variability in 105 SDSS quasars (Wilhite+, 2006) J/ApJS/165/1 : BAL QSOs from SDSS DR3 (Trump+, 2006) J/MNRAS/410/860 : Redshift dependence of BAL QSOs (Allen+, 2011) J/A+A/548/A66 : SDSS Quasar Catalog, DR9Q (Paris+, 2012) J/ApJ/763/37 : Metals in SDSS QSOs. I. 1.5