Astrophys.J. 606 (2004) 741-748 By observing the high galactic latitude equatorial sky in drift scan mode
with the QUEST (QUasar Equatorial Survey Team) Phase 1 camera, multi-bandpass
photometry on a ...large strip of sky, resolved over a large range of time scales
(from hourly to biennially) has been collected. A robust method of ensemble
photometry revealed those objects within the scan region that fluctuate in
brightness at a statistically significant level. Subsequent spectroscopic
observations of a subset of those varying objects easily discriminated the
quasars from stars. For a 13-month time scale, 38% of the previously known
quasars within the scan region were seen to vary in brightness and subsequent
spectroscopic observation revealed that approximately 7% of all variable
objects in the scan region are quasars. Increasing the time baseline to 26
months increased the percentage of previously known quasars which vary to 61%
and confirmed via spectroscopy that 7% of the variable objects in the region
are quasars. This reinforces previously published trends and encourages
additional and ongoing synoptic searches for new quasars and their subsequent
analysis. During two spectroscopic observing campaigns, a total of 30 quasars
were confirmed, 11 of which are new discoveries and 19 of which were determined
to be previously known. Using the previously cataloged quasars as a benchmark,
we have found it possible to better optimize future variability surveys. This
paper reports on the subset of variable objects which were spectroscopically
confirmed as quasars.
We study the large-scale spatial distribution of low-redshift quasars and
Seyfert~1 galaxies using a sample of 106 luminous emission-line objects
($\bar{M}_{B} \approx -23$) selected by their ...H$\alpha$ emission lines in a
far-red objective prism survey ($0.2 < z < 0.37$). Of the 106 objects, 25 were
previously known AGN (Veron-Cetty and Veron 2000), and follow-up spectroscopy
for an additional 53 objects (including all object pairs with separation $r <
20 \hmpc$) confirmed 48 AGN and 5 narrow emission-line galaxies (NELGs). The
calculated amplitude of the spatial two-point correlation function for the
emission-line sample is $A = 0.4 \cdot \bar{\xi}(r < 20 \hmpc) \cdot 20^{1.8} =
142 \pm 53$. Eliminating the confirmed NELGs from the sample we obtain the AGN
clustering amplitude $A = 98 \pm 54$. Using Monte Carlo simulations we reject
the hypothesis that the observed pair counts were drawn from a random
distribution at the 99.97% and 98.6% confidence levels for the entire sample
and the AGN subset respectively. We measure a decrease in the quasar clustering
amplitude by a factor of $3.7 \pm 2.0$ between $z = 0.26$ and $z \approx 1.5$,
and present the coordinates, redshifts, and follow-up spectroscopy for the 15
previously unknown AGN and 4 luminous NELGs that contribute to the clustering
signal.
We study the large-scale spatial distribution of low-redshift quasars and Seyfert~1 galaxies using a sample of 106 luminous emission-line objects (\(\bar{M}_{B} \approx -23\)) selected by their ...H\(\alpha\) emission lines in a far-red objective prism survey (\(0.2 < z < 0.37\)). Of the 106 objects, 25 were previously known AGN (Veron-Cetty and Veron 2000), and follow-up spectroscopy for an additional 53 objects (including all object pairs with separation \(r < 20 \hmpc\)) confirmed 48 AGN and 5 narrow emission-line galaxies (NELGs). The calculated amplitude of the spatial two-point correlation function for the emission-line sample is \(A = 0.4 \cdot \bar{\xi}(r < 20 \hmpc) \cdot 20^{1.8} = 142 \pm 53\). Eliminating the confirmed NELGs from the sample we obtain the AGN clustering amplitude \(A = 98 \pm 54\). Using Monte Carlo simulations we reject the hypothesis that the observed pair counts were drawn from a random distribution at the 99.97% and 98.6% confidence levels for the entire sample and the AGN subset respectively. We measure a decrease in the quasar clustering amplitude by a factor of \(3.7 \pm 2.0\) between \(z = 0.26\) and \(z \approx 1.5\), and present the coordinates, redshifts, and follow-up spectroscopy for the 15 previously unknown AGN and 4 luminous NELGs that contribute to the clustering signal.
Astron.J.131:1923-1933,2006 We present variability and multi-wavelength photometric information for the
933 known quasars in the QUEST Variability Survey. These quasars are grouped
into variable and ...non-variable populations based on measured variability
confidence levels. In a time-limited synoptic survey, we detect an
anti-correlation between redshift and the likelihood of variability. Our
comparison of variability likelihood to radio, IR, and X-ray data is consistent
with earlier quasar studies. Using already-known quasars as a template, we
introduce a light curve morphology algorithm that provides an efficient method
for discriminating variable quasars from periodic variable objects in the
absence of spectroscopic information. The establishment of statistically robust
trends and efficient, non-spectroscopic selection algorithms will aid in quasar
identification and categorization in upcoming massive synoptic surveys.
Finally, we report on three interesting variable quasars, including variability
confirmation of the BL Lac candidate PKS 1222+037.
By observing the high galactic latitude equatorial sky in drift scan mode with the QUEST (QUasar Equatorial Survey Team) Phase 1 camera, multi-bandpass photometry on a large strip of sky, resolved ...over a large range of time scales (from hourly to biennially) has been collected. A robust method of ensemble photometry revealed those objects within the scan region that fluctuate in brightness at a statistically significant level. Subsequent spectroscopic observations of a subset of those varying objects easily discriminated the quasars from stars. For a 13-month time scale, 38% of the previously known quasars within the scan region were seen to vary in brightness and subsequent spectroscopic observation revealed that approximately 7% of all variable objects in the scan region are quasars. Increasing the time baseline to 26 months increased the percentage of previously known quasars which vary to 61% and confirmed via spectroscopy that 7% of the variable objects in the region are quasars. This reinforces previously published trends and encourages additional and ongoing synoptic searches for new quasars and their subsequent analysis. During two spectroscopic observing campaigns, a total of 30 quasars were confirmed, 11 of which are new discoveries and 19 of which were determined to be previously known. Using the previously cataloged quasars as a benchmark, we have found it possible to better optimize future variability surveys. This paper reports on the subset of variable objects which were spectroscopically confirmed as quasars.
We present variability and multi-wavelength photometric information for the 933 known quasars in the QUEST Variability Survey. These quasars are grouped into variable and non-variable populations ...based on measured variability confidence levels. In a time-limited synoptic survey, we detect an anti-correlation between redshift and the likelihood of variability. Our comparison of variability likelihood to radio, IR, and X-ray data is consistent with earlier quasar studies. Using already-known quasars as a template, we introduce a light curve morphology algorithm that provides an efficient method for discriminating variable quasars from periodic variable objects in the absence of spectroscopic information. The establishment of statistically robust trends and efficient, non-spectroscopic selection algorithms will aid in quasar identification and categorization in upcoming massive synoptic surveys. Finally, we report on three interesting variable quasars, including variability confirmation of the BL Lac candidate PKS 1222+037.
Astrophys.J.554:L33-L36,2001 We have measured the periods and light curves of 148 RR Lyrae variables from
V=13.5 to 19.7 from the first 100 sq. degrees of the QUEST RR Lyrae survey.
Approximately 55% ...of these stars belong to the clump of stars detected earlier
by the Sloan Digital Sky Survey. According to our measurements, this feature
has ~10 times the background density of halo stars, spans at least 37.5 deg by
3.5 deg in right ascension and declination (>=30 by >=3 kpc), lies ~50 kpc from
the Sun, and has a depth along the line of sight of ~5 kpc (1 sigma). These
properties are consistent with the recent models that suggest it is a tidal
stream from the Sgr dSph galaxy. The mean period of the type ab variables, 0.58
d, is also consistent. In addition, we have found two smaller over-densities in
the halo, one of which may be related to the globular cluster Pal 5.
Astrophys.J. 548 (2001) L243-L248 We describe the discovery circumstances and photometric properties of 2000
EB173, now one of the brightest trans-Neptunian objects (TNOs) with opposition
magnitude ...m_R=18.9 and also one of the largest Plutinos, found with the
drift-scanning camera of the QUEST Collaboration, attached to the 1-m Schmidt
telescope of the National Observatory of Venezuela. We measure B-V = 0.99 +/-
0.14 and V-R = 0.57 +/- 0.05, a red color observed for many fainter TNOs. At
our magnitude limit m_R = 20.1 +/- 0.20, our single detection reveals a sky
density of 0.015 (+0.034, -0.012) TNOs per deg^2 (the error bars are 68%
confidence limits), consistent with fainter surveys showing a cumulative number
proportional to 10^0.5m_R. Assuming an inclination distribution of TNOs with
FWHM exceeding 30 deg, it is likely that one hundred to several hundred objects
brighter than m_R=20.1 remain to be discovered.
The optical transient of the faint Gamma Ray Burst 990308 was detected by the
QUEST camera on the Venezuelan 1-m Schmidt telescope starting 3.28 hours after
the burst. Our photometry gives $V = 18.32 ...\pm 0.07$, $R = 18.14 \pm 0.06$, $B
= 18.65 \pm 0.23$, and $R = 18.22 \pm 0.05$ for times ranging from 3.28 to 3.47
hours after the burst. The colors correspond to a spectral slope of close to
$f_{\nu} \propto \nu^{1/3}$. Within the standard synchrotron fireball model,
this requires that the external medium be less dense than $10^{4} cm^{-3}$, the
electrons contain $> 20%$ of the shock energy, and the magnetic field energy
must be less than 24% of the energy in the electrons for normal interstellar or
circumstellar densities. We also report upper limits of $V > 12.0$ at 132 s
(with LOTIS), $V > 13.4$ from 132-1029s (with LOTIS), $V > 15.3$ at 28.2 min
(with Super-LOTIS), and a 8.5 GHz flux of $< 114 \mu Jy$ at 110 days (with the
Very Large Array). WIYN 3.5-m and Keck 10-m telescopes reveal this location to
be empty of any host galaxy to $R > 25.7$ and $K > 23.3$. The lack of a host
galaxy likely implies that it is either substantially subluminous or more
distant than a red shift of $\sim 1.2$.
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