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

Kim, Sanghyuk; Jeon, Yiseul; Lee, Hye-In; Park, Woojin; Ji, Tae-Geun; Hyun, Minhee; Choi, Changsu; Im, Myungshin; Pak, Soojong

doi:10.1088/1538-3873/128/969/115004

Cited by 9 publications

(6 citation statements)

References 39 publications

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“…In addition to this, we developed the SED Camera for Quasars in EArly uNiverse (SQUEAN; Kim et al 2016;Choi et al 2015), as an upgraded instrument of the Camera for Quasars in EArly uNiverse (CQUEAN; Park et al 2012;Kim et al 2011;Lim et al 2013), on the 2.1 m Otto Struve Telescope of McDonald Observatory. This new instrument works with 20 filters consisting of broad-band filters (e.g., griz) and 50 nm medium bandwidth filters of which the central wavelengths range 675 to 1025 nm (m675-m1025 1 ).…”

Section: Introductionmentioning

confidence: 99%

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

Kim

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.

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Section: Introductionmentioning

confidence: 99%

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

Kim

Jeon

et al. 2019

ApJ

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“…Compared to the broadbands with widths of ∼ 1500 Å, the medium-bands can improve the spectral sampling by a factor of 3, and hence the better quasar selection can be achieved. The medium-band observations were conducted using the SED camera for QUasars in EArly uNiverse (SQUEAN) on the 2.1-m Otto-Struve telescope at Mcdonald Observatory (Park et al 2012;Kim et al 2016) and Seoul National University 4K x 4K Camera (SNUCAM) on the 1.5-m telescope at Maidanak Observatory (Im et al 2010). The data were taken with the seeing condition better than 1.…”

Section: Medium-band Datamentioning

confidence: 99%

The Infrared Medium-deep Survey. \Romannum{7}. Faint Quasars at $z \sim 5$ in the ELAIS-N1 Field

Shin,

Im,

Kim

et al. 2020

Preprint

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The intergalactic medium (IGM) at z ∼ 5 to 6 is largely ionized, and yet the main source for the IGM ionization in the early universe is uncertain. Of the possible contributors are faint quasars with −26 M 1450 −23, but their number density is poorly constrained at z ∼ 5. In this paper, we present our survey of faint quasars at z ∼ 5 in the European Large-Area ISO Survey-North 1 (ELAIS-N1) field over a survey area of 6.51 deg 2 and examine if such quasars can be the dominant source of the IGM ionization. We use the deep optical/near-infrared data of the ELAIS-N1 field as well as the additional medium-band observations to find z ∼ 5 quasars through a two-step approach using the broadband color selection, and SED fitting with the medium-band information included. Adopting Bayesian information criterion, we identify ten promising quasar candidates. Spectra of three of the candidates are obtained, confirming all of them to be quasars at z ∼ 5 and supporting the reliability of the quasar selection. Using the promising candidates, we derive the z ∼ 5 quasar luminosity function at −26 M 1450 −23. The number density of faint z ∼ 5 quasars in the ELAIS-N1 field is consistent with several previous results that quasars are not the main contributors to the IGM-ionizing photons at z ∼ 5.

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“…To narrow down the number of plausible z ∼ 5 quasar candidates, follow-up observations of these broadbandselected candidates were carried out in medium bands with the SED Camera for Quasars in Early Universe (SQUEAN; Choi et al 2015;Kim et al 2016) on the Otto Struve 2.1 m Telescope at McDonald Observatory. At z ∼ 5, the Lyα λ1216 line is located at ∼ 7300 Å, so we have obtained m675, m725, and m775 images, where the filter names are chosen by combining "m" for medium-band and the number of the central wavelength of the filter in nanometers.…”

Section: Squean Follow-up Imaging In Medium Bandsmentioning

confidence: 99%

The Infrared Medium-deep Survey. VIII. Quasar Luminosity Function at $z\sim5$

Kim,

Im,

Jeon

et al. 2020

Preprint

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Faint z ∼ 5 quasars with M 1450 ∼ −23 mag are known to be the potentially important contributors to the ultraviolet ionizing background in the post-reionization era. However, their number density has not been well determined, making it difficult to assess their role in the early ionization of the intergalactic medium (IGM). In this work, we present the updated results of our z ∼ 5 quasar survey using the Infrared Medium-deep Survey (IMS), a near-infrared imaging survey covering an area of 85 deg 2 . From our spectroscopic observations with the Gemini Multi-Object Spectrograph (GMOS) on the Gemini-South 8 m Telescope, we discovered eight new quasars at z ∼ 5 with −26.1 ≤ M 1450 ≤ −23.3. Combining our IMS faint quasars (M 1450 > −27 mag) with the brighter Sloan Digital Sky Survey (SDSS) quasars (M 1450 < −27 mag), we derive the z ∼ 5 quasar luminosity function (QLF) without any fixed parameters down to the magnitude limit of M 1450 = −23 mag. We find that the faint-end slope of the QLF is very flat (α = −1.2 +1.4 −0.6 ), with a characteristic luminosity of M * 1450 = −25.8 +1.4 −1.1 mag. The number density of z ∼ 5 quasars from the QLF gives an ionizing emissivity at 912 Å of 912 = (3.7-7.1) × 10 23 erg s −1 Hz −1 Mpc −3 and an ionizing photon density of ṅion = (3.0-5.7) × 10 49Mpc −3 s −1 . These results imply that quasars are responsible for only 10-20% (up to 50% even in the extreme case) of the photons required to completely ionize the IGM at z ∼ 5, disfavoring the idea that quasars alone could have ionized the IGM at z ∼ 5.

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

Cited by 9 publications

References 39 publications

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

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

The Infrared Medium-deep Survey. \Romannum{7}. Faint Quasars at $z \sim 5$ in the ELAIS-N1 Field

The Infrared Medium-deep Survey. VIII. Quasar Luminosity Function at $z\sim5$

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