We present the North Galactic Cap sample of the Extremely Luminous Quasar Survey (ELQS-N), which targets quasars with M1450 < −27 at 2.8 ≤ z < 5 in an area of ∼7600 deg2 of the Sloan Digital Sky ...Survey (SDSS) footprint with 90° < R.A. < 270°. Based on a near-infrared/infrared JKW2 color cut, the ELQS selection efficiently uses random forest methods to classify quasars and to estimate photometric redshifts; this scheme overcomes some of the difficulties of pure optical quasar selection at z 3. As a result, we retain a completeness of >70% over z ∼ 3.0-5.0 at mi 17.5, limited toward fainter magnitudes by the depth of the Two Micron All Sky Survey. The presented quasar catalog consists of a total of 270 objects, of which 39 are newly identified in this work with spectroscopy obtained at the Vatican Advanced Technology Telescope and the MMT 6.5 m telescope. In addition to the high completeness, which allowed us to discover new quasars in the already well-surveyed SDSS North Galactic Cap, the efficiency of our selection is relatively high at ∼79%. Using 120 objects of this quasar sample we are able to extend the previously measured optical quasar luminosity function (QLF) by one magnitude toward the bright end at 2.8 ≤ z ≤ 4.5. A first analysis of the QLF suggests a relatively steep bright-end slope of β −4 for this sample. This result contrasts with previous results in the same redshift range, which find a much flatter slope around β ∼ −2.5, but agrees with recent measurements of the bright-end slope at lower and higher redshifts. Our results constrain the bright-end slope at z = 2.8-4.5 to β < −2.94 with a 99% confidence.
Context.
Planetary systems and debris discs are natural by-products of the star formation process, and they affect each other. The direct imaging technique allows simultaneous imaging of both a ...companion and the circumstellar disc it resides in, and is thus a valuable tool to study companion-disc interactions. However, the number of systems in which a companion and a disc have been detected at the same time remains low.
Aims.
Our aim is to increase this sample, and to continue detecting and studying the population of giant planets in wide orbits.
Methods.
We carry out the
L
′ band Imaging Survey for Exoplanets in the North (LIStEN), which targeted 28 nearby stars: 24 are known to harbour a debris disc (DD) and the remaining 4 are protoplanetary disc-hosting stars. We aim to detect possible new companions, and study the interactions between the companion and their discs. Angular differential imaging observations were carried out in the
L
′ band at 3.8
μ
m using the LMIRCam instrument at the LBT, between October 2017 and April 2019.
Results.
No new companions were detected. We combined the derived mass detection limits with information on the disc, and on the proper motion of the host star, to constrain the presence of unseen planetary and low-mass stellar companion around the 24 disc-hosting stars in our survey. We find that 2 have an uncertain DD status and the remaining 22 have disc sizes compatible with self-stirring. Three targets show a proper motion anomaly (PMa) compatible with the presence of an unseen companion.
Conclusions.
Our achieved mass limits combined with the PMa analysis for HD 113337 support the presence of a second companion around the star, as suggested in previous RV studies. Our mass limits also help to tighten the constraints on the mass and semi-major axis of the unseen companions around HD 161868 and HD 8907.
Theoretical studies suggest that a giant planet around the young star MWC 758 could be responsible for driving the spiral features in its circumstellar disk. Here, we present a deep imaging campaign ...with the Large Binocular Telescope with the primary goal of imaging the predicted planet. We present images of the disk in two epochs in the L′ filter (3.8 m) and a third epoch in the M′ filter (4.8 m). The two prominent spiral arms are detected in each observation, which constitute the first images of the disk at M′, and the deepest yet in L′ (ΔL′ = 12.1 exterior to the disk at 5 significance). We report the detection of an S/N ∼ 3.9 source near the end of the Southern arm, and, from the source's detection at a consistent position and brightness during multiple epochs, we establish a ∼90% confidence-level that the source is of astrophysical origin. We discuss the possibilities that this feature may be (a) an unresolved disk feature, and (b) a giant planet responsible for the spiral arms, with several arguments pointing in favor of the latter scenario. We present additional detection limits on companions exterior to the spiral arms, which suggest that a 4 MJup planet exterior to the spiral arms could have escaped detection. Finally, we do not detect the companion candidate interior to the spiral arms reported recently by Reggiani et al., although forward modeling suggests that such a source would have likely been detected.
ABSTRACT
RR Lyrae stars play a central role in tracing phase-space structures within the Milky Way because they are easy to identify, are relatively luminous, and are found in large numbers in the ...Galactic bulge, disc, and halo. In this work, we present a new set of spectroscopic metallicity calibrations that use the equivalent widths of the Ca ii K and Balmer H γ and H δ lines to calculate metallicity values from low-resolution spectra. This builds on an earlier calibration from Layden by extending the range of equivalent widths which map between Ca ii K and the Balmer lines. We have developed the software rrlfe to apply this calibration to spectra in a consistent, reproducible, and extensible manner. This software is open-source and available to the community. The calibration can be updated with additional data sets in the future.
Monitoring the long-term radial velocity (RV) and acceleration of nearby stars has been proven as an effective method for directly detecting binary and substellar companions. Some fraction of nearby ...RV trend systems are expected to be comprised of compact objects that likewise induce a systemic Doppler signal. In this paper, we report the discovery of a white dwarf (WD) companion found to orbit the nearby (π = 28.297 0.066 mas) G9 V star HD 169889. High-contrast imaging observations using NIRC2 at the W. M. Keck Observatory and LMIRCam at the Large Binocular Telescope (LBT) Observatory uncover the (ΔH = 9.76 0.16, ΔL′ = 9.60 0.03) companion at an angular separation of 0 8 (28 au). Thirteen years of precise Doppler observations reveal a steep linear acceleration in the RV time series and place a dynamical constraint on the companion mass of M ≥ 0.369 0.010 M . This "Sirius-like" system adds to the census of WD companions suspected to be missing from surveys of in the solar neighborhood.
This work demonstrates the use of two different observing modes with the twin apertures of the LBT. One pointing mode involves the incoherent juxtaposition of two filled-aperture PSFs to perform ...differential photometry in the thermal infrared. This is "wall-eyed" pointing, which is used to perform differential photometry on three sets of test targets. To test the possibility of applying this to the study of atmospheres of low-mass objects, one of the targets involves an exoplanet transit in front of its host star, and another involves a secondary occultation. Though the photometric precision in differential mode is increased compared to single-aperture mode, it remains limited by line-of-sight systematics possibly stemming from water vapor variations. The remainder (and majority) of the thesis involves the long-anticipated Fizeau mode---the coherent and multiaxial combination of the LBT beams. Compared to a single filled aperture, the Fizeau mode can generate a PSF that can in principle increase the resolution by a factor of ~3 along the long baseline. A number of technical challenges are described, and a science dataset of a nearby star in Fizeau mode is reduced in a first-ever trial of this mode to perform high-contrast imaging. The PSF remains unstable, particularly in phase. A new codebase was written to perform the requisite angular differential imaging of a Fizeau PSF with highly time-dependent optical aberrations. I describe the results of this process and outline avenues of possible future work.
We present the first L-band (2.8-4.1 m) spectroscopy of κ Andromedae b, a ∼20 MJup companion orbiting at 1″ projected separation from its B9-type stellar host. We combine our Large Binocular ...Telescope (LBT) Arizona Lenslets for Exoplanet Spectroscopy (ALES) integral field spectrograph data with measurements from other instruments to analyze the atmosphere and physical characteristics of κ And b. We report a discrepancy of ∼20% (2 ) in the L′ flux of κ And b when comparing to previously published values. We add an additional L′ constraint using an unpublished imaging data set collected in 2013 using the LBT Interferometer/LMIRCam, the instrument in which the ALES module has been built. The LMIRCam measurement is consistent with the ALES measurement, both suggesting a fainter L-band scaling than previous studies. The data, assuming the flux scaling measured by ALES and LMIRCam imaging, are well fit by an L3-type brown dwarf. Atmospheric model fits to measurements spanning 0.9-4.8 m reveal some tension with the predictions of evolutionary models, but the proper choice of cloud parameters can provide some relief. In particular, models with clouds extending to very low pressures composed of grains ≤1 m appear to be necessary. If the brighter L′ photometry is accurate, there is a hint that subsolar metallicity may be required.
Time-series photometry taken from ground-based facilities is improved with the use of comparison stars due to the short timescales of atmospheric-induced variability. However, the sky is bright in ...the thermal infrared (3-5 m), and the correspondingly small fields of view of available detectors make it highly unusual to have a calibration star in the same field as a science target. Here, we present a new method of obtaining differential photometry by simultaneously imaging a science target and a calibrator star, separated by 2 amin, onto a 10 × 10 asec2 field-of-view detector. We do this by taking advantage of the Large Binocular Telescope's (LBT) unique binocular design to point the two co-mounted telescopes apart and simultaneously obtain both targets in three sets of observations. Results indicate that the achievable scatter in LS-band ( λ c = 3.3 m) is at the percent level for bright targets and possibly better with heavier sampling and characterization of the systematics.
Time-series photometry taken from ground-based facilities is improved with the use of comparison stars due to the short timescales of atmospheric-induced variability. However, the sky is bright in ...the thermal infrared (3–5 μm), and the correspondingly small fields of view of available detectors make it highly unusual to have a calibration star in the same field as a science target. Here, we present a new method of obtaining differential photometry by simultaneously imaging a science target and a calibrator star, separated by ≲2 amin, onto a 10 × 10 asec² field-of-view detector. We do this by taking advantage of the Large Binocular Telescope’s (LBT) unique binocular design to point the two co-mounted telescopes apart and simultaneously obtain both targets in three sets of observations. Results indicate that the achievable scatter in LS
-band (λc
= 3.3 μm) is at the percent level for bright targets and possibly better with heavier sampling and characterization of the systematics.
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