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We study the mass of quasar-hosting dark matter halos at z $sim$ 6 and further constrain the fraction of dark matter halos hosting an active quasar $f_{on}$ and the quasar beaming angle $i_{rm max}$ using observations of CII lines in the literature. We make assumptions that (1) more massive halos host brighter quasars, (2) a fraction of the halos host active quasars with a certain beaming angle, (3) cold gas in galaxies has rotational velocity $V_{rm circ}=alpha V_{rm max}$, and that (4) quasars point randomly on the sky. We find that for a choice of specific $alpha gtrsim 1$, the most likely solution has $f_{rm on} < 0.01$, corresponding to a small duty cycle of quasar activity. However, if we marginalize over $alpha$, for some choices of a prior a second solution with $f_{rm on}=1$ appears. Overall, our the constraints are highly sensitive to $alpha$ and hence inconclusive. Stronger constraints on $f_{rm on}$ can be made if we better understand the dynamics of cold gas in these galaxies.
Significant clustering around the rarest luminous quasars is a feature predicted by dark matter theory combined with number density matching arguments. However, this expectation is not reflected by observations of quasars residing in a diverse range
We searched for high-z quasars within the X-ray source population detected in the contiguous $sim 140^2$ eFEDS field observed by eROSITA during the performance verification phase. We collected the available spectroscopic information in the field, inc
We search for galaxies with a strong Balmer break (Balmer Break Galaxies; BBGs) at $z sim 6$ over a 0.41 deg$^2$ effective area in the COSMOS field. Based on rich imaging data, including data obtained with the Atacama Large Millimeter/submillimeter A
We investigate the infrared (IR) emission of high-redshift ($zsim 6$), highly star-forming (${ {rm SFR} > 100}$ $M_{rm odot} {rm yr}^{-1}$) galaxies, with/without Active Galactic Nuclei (AGN), using a suite of cosmological simulations featuring dust
We present Atacama Large Millimiter/submillimiter Array (ALMA) observations of eight highly excited CO (J$_{rm up}>8$) lines and continuum emission in two $zsim6$ quasars: SDSS J231038.88+185519.7 (hereafter J2310), for which CO(8-7), CO(9-8), and CO