%0 Generic %1 pacucci2019reality %A Pacucci, Fabio %A Loeb, Abraham %D 2019 %K library %T Reality or Mirage? Observational Test and Implications for the Claimed Extremely Magnified Quasar at $z = 6.3$ %U http://arxiv.org/abs/1910.10156 %X In the last two decades $200$ quasars have been discovered at $z>6$, hosting active super-massive black holes with masses $M_\bullet 10^9 \,M_ødot$. While these sources reflect only the tip of the iceberg of the black hole mass distribution, their detection challenges standard growth models. The most massive $z>6$ black hole that was inferred thus far (J0100+2802, $M_\bullet 1.210^10 \,M_ødot$) was recently claimed to be lensed, with a magnification factor $\mu=450$. Here we perform a consistency check of this claim, finding that the detection of such source requires a bright-end slope $3.6$ for the intrinsic quasar luminosity function, $\Phi(L) L^-\beta$. Commonly used values of $2.8$ are rejected at $>3\sigma$. If the claim is confirmed, it is very unlikely that all the remaining $51$ sources in the SDSS sample are not magnified. Furthermore, it suffices that $25\%$ of the remaining sources are lensed for the intrinsic luminosity function to differ significantly (i.e., $>3\sigma$) from the observed one. The presence of additional extremely magnified sources in the sample would lower the requirement to $4\%$. Our results urge the community to perform more extended multi-wavelength searches targeting $z>6$ lensed quasars, also among known samples. This effort could vitally contribute to solve the open problem of the growth of the brightest $z7$ quasars.

@misc{pacucci2019reality, abstract = {In the last two decades $\sim 200$ quasars have been discovered at $z>6$, hosting active super-massive black holes with masses $M_{\bullet} \gtrsim 10^9 \,{\rm M_\odot}$. While these sources reflect only the tip of the iceberg of the black hole mass distribution, their detection challenges standard growth models. The most massive $z>6$ black hole that was inferred thus far (J0100+2802, $M_{\bullet} \approx 1.2\times 10^{10} \,{\rm M_\odot}$) was recently claimed to be lensed, with a magnification factor $\mu=450$. Here we perform a consistency check of this claim, finding that the detection of such source requires a bright-end slope $\beta \gtrsim 3.6$ for the intrinsic quasar luminosity function, $\Phi(L) \propto L^{-\beta}$. Commonly used values of $\beta \sim 2.8$ are rejected at $>3\sigma$. If the claim is confirmed, it is very unlikely that all the remaining $51$ sources in the SDSS sample are not magnified. Furthermore, it suffices that $\gtrsim 25\%$ of the remaining sources are lensed for the intrinsic luminosity function to differ significantly (i.e., $>3\sigma$) from the observed one. The presence of additional extremely magnified sources in the sample would lower the requirement to $\sim 4\%$. Our results urge the community to perform more extended multi-wavelength searches targeting $z>6$ lensed quasars, also among known samples. This effort could vitally contribute to solve the open problem of the growth of the brightest $z\sim 7$ quasars.}, added-at = {2019-10-24T10:51:12.000+0200}, author = {Pacucci, Fabio and Loeb, Abraham}, biburl = {https://www.bibsonomy.org/bibtex/2abedd24ffa8d6770903c3d1db730244e/gpkulkarni}, description = {Reality or Mirage? Observational Test and Implications for the Claimed Extremely Magnified Quasar at $z = 6.3$}, interhash = {846af269597ce6f984c3fc81b2893435}, intrahash = {abedd24ffa8d6770903c3d1db730244e}, keywords = {library}, note = {cite arxiv:1910.10156Comment: 7 pages, 3 figures. Submitted to ApJ Letters}, timestamp = {2019-10-24T10:51:12.000+0200}, title = {Reality or Mirage? Observational Test and Implications for the Claimed Extremely Magnified Quasar at $z = 6.3$}, url = {http://arxiv.org/abs/1910.10156}, year = 2019 }