THE INFRARED MEDIUM-DEEP SURVEY. V. A NEW SELECTION STRATEGY FOR QUASARS AT z &gt; 5 BASED ON MEDIUM-BAND OBSERVATIONS WITH SQUEAN

Jeon

et al. 2019

ApJ

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The faint quasars with M 1450 > −24 mag are known to hold the key to the determination of the ultraviolet emissivity for the cosmic re-ionization. But only a few have been identified so far because of the limitations on the survey data. Here, we present the first results of the z ∼ 5 faint quasar survey with the Infrared Medium-deep Survey (IMS), which covers ∼ 100 deg 2 areas in J-band to the depths of J AB ∼ 23 mag. To improve selection methods, the medium-band follow-up imaging has been carried out using the SED camera for QUasars in Early uNiverse (SQUEAN) on the Otto Struve 2.1 m Telescope. The optical spectra of the candidates were obtained with 8-m class telescopes. We newly discovered 10 quasars with −25 < M 1450 < −23 at z ∼ 5, among which three have been missed in a previous survey using the same optical data over the same area, implying the necessity for improvements in high redshift faint quasars selection. We derived photometric redshifts from the medium-band data, and find that they have high accuracies of |∆z|/(1 + z) = 0.016. The mediumband-based approach allows us to rule out many of the interlopers that contaminate 20 % of the broad-band-selected quasar candidates. These results suggest that the medium-band-based approach is a powerful way to identify z ∼ 5 quasars and measure their redshifts at high accuracy (1-2 %). It is also a cost-effective way to understand the contribution of quasars to the cosmic re-ionization history. dreds of them being at high redshift of z 5 (Fan et al.1 The medium-band filters are named as m (initial of the medium-band) + the central wavelength of the filter in nm.

Section: Medium-band Color Selection and Its Efficiencysupporting

confidence: 63%

Section: Broad-band Color Selectionmentioning

confidence: 99%

Section: Medium-band Observationmentioning

confidence: 99%

Section: Medium-band Observationmentioning

confidence: 99%

“…The other symbols are identical to those in Figure 2. We followed the color selection criteria with medium-bands suggested by Jeon et al (2016):…”

Section: Medium-band Observationmentioning

confidence: 99%

See 3 more Smart Citations

The Infrared Medium-deep Survey. VI. Discovery of Faint Quasars at z ∼ 5 with a Medium-band-based Approach

Jeon

et al. 2019

ApJ

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High-z Universe probed via Lensing by QSOs (HULQ)

Taak

et al. 2022

A&A

Galaxies and their central supermassive black holes are known to coevolve, but the physical background for this is unknown as of yet. The High-z Universe probed via Lensing by QSOs (HULQ) project aims to investigate this coevolution by using quasi-stellar object (QSO) host galaxies acting as gravitational lenses (QSO lenses). We present the results of the spectroscopic observation of the first QSO lens candidate from the HULQ project, HULQ J0002+0239, which consists of a QSO host galaxy at z d = 1.455 and four seemingly lensed objects in a cross-like configuration. Deep optical spectra of two of the possibly lensed objects with z ∼ 24.5 mag were obtained with the Gemini Multi-Object Spectrograph on the Gemini North Telescope. Their spectra reveal that the objects are newly discovered galaxies at z = 0.29 and z = 1.11, and we conclude that HULQ J0002+0239 is not a QSO lens. Our QSO lens search results are so far in agreement with the predicted number of QSO lenses, and we discuss how the future investigation of additional QSO lens candidates could tell us more about the evolution of the black hole mass and host galaxy scaling relations.

Development of SED Camera for Quasars in Early Universe (SQUEAN)

Jeon

Lee

et al. 2016

PASP

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We describe the characteristics and performance of a camera system, Spectral energy distribution Camera for Quasars in Early Universe (SQUEAN). It was developed to measure SEDs of high redshift quasar candidates (z 5) and other targets, e.g., young stellar objects, supernovae, and gamma-ray bursts, and to trace the time variability of SEDs of objects such as active galactic nuclei (AGNs).SQUEAN consists of an on-axis focal plane camera module, an auto-guiding system, and mechanical supporting structures. The science camera module is composed of a focal reducer, a customizable filter wheel, and a CCD camera on the focal plane. The filter wheel uses filter cartridges that can house filters with different shapes and sizes, enabling the filter wheel to hold twenty filters of 50 mm × 50 mm size, ten filters of 86 mm × 86 mm size, or many other combinations. The initial filter mask was applied to calibrate the filter wheel with high accuracy and we verified that the filter position is repeatable at much less than one pixel accuracy. We installed and tested 50 nm medium bandwidth filters of 600 -1,050 nm and other filters at the commissioning observation in 2015 February. We found that SQUEAN can reach limiting magnitudes of 23.3 -25.3 AB mag at 5-σ in a 1-hour total integration time.