Iron-corrected Single-epoch Black Hole Masses of DESI Quasars at low redshift
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2025
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| author | Pan, Zhiwei Jiang, Linhua Guo, Wei-Jian Sun, Shengxiu Siudek, Małgorzata Aguilar, Jessica Nicole Ahlen, Steven Brooks, David Claybaugh, Todd de la Macorra, Axel Doel, Peter Gaztañaga, Enrique Gontcho, Satya Gontcho A Juneau, Stephanie Kisner, Theodore Lambert, Andrew Landriau, Martin Guillou, Laurent Le Manera, Marc Martini, Paul Meisner, Aaron Miquel, Ramon Moustakas, John Myers, Adam Poppett, Claire Prada, Francisco Rossi, Graziano Sanchez, Eusebio Schubnell, Michael Seo, Hee-Jong Sprayberry, David Tarlé, Gregory Weaver, Benjamin Alan Zou, Hu |
| author_facet | Pan, Zhiwei Jiang, Linhua Guo, Wei-Jian Sun, Shengxiu Siudek, Małgorzata Aguilar, Jessica Nicole Ahlen, Steven Brooks, David Claybaugh, Todd de la Macorra, Axel Doel, Peter Gaztañaga, Enrique Gontcho, Satya Gontcho A Juneau, Stephanie Kisner, Theodore Lambert, Andrew Landriau, Martin Guillou, Laurent Le Manera, Marc Martini, Paul Meisner, Aaron Miquel, Ramon Moustakas, John Myers, Adam Poppett, Claire Prada, Francisco Rossi, Graziano Sanchez, Eusebio Schubnell, Michael Seo, Hee-Jong Sprayberry, David Tarlé, Gregory Weaver, Benjamin Alan Zou, Hu |
| contents | We present a study on the possible overestimation of single-epoch supermassive black hole (SMBH) masses in previous works, based on more than 55,000 type 1 quasars at $0.25 < z < 0.8$ from the Dark Energy Spectroscopic Instrument (DESI). We confirm that iron emission strength serves as a good tracer of the Eddington ratio, and estimate SMBH masses using an iron-corrected $R$-$L$ relation for H$β$, where $R$ is the broad line region size and $L$ is the continuum luminosity. Compared to our measurements, previous canonical measurements without the iron correction are overestimated by a factor of 1.5 on average. The overestimation can be up to a factor of 5 for super-Eddington quasars. The fraction of super-Eddington quasars in our sample is about 5%, significantly higher than 0.4% derived from the canonical measurements. Using a sample featuring both H$β$ and MgII emission lines, we calibrate MgII-based SMBH masses using iron-corrected, H$β$-based SMBH masses and establish an iron-corrected $R$-$L$ relation for MgII. The new relation adds an extra term of $-0.34R_{\mathrm{Fe}}$ to the $R$-$L$ relation, where $R_{\mathrm{Fe}}$ denotes the relative iron strength. We use this formula to build a catalog of about 0.5 million DESI quasars at $0.6<z<1.6$. If these iron-corrected $R$-$L$ relations for H$β$ and MgII are valid at high redshift, current mass measurements of luminous quasars at $z\ge6$ would have been overestimated by a factor of 2.3 on average, alleviating the tension between SMBH mass and growth history in the early universe. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_03684 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Iron-corrected Single-epoch Black Hole Masses of DESI Quasars at low redshift Pan, Zhiwei Jiang, Linhua Guo, Wei-Jian Sun, Shengxiu Siudek, Małgorzata Aguilar, Jessica Nicole Ahlen, Steven Brooks, David Claybaugh, Todd de la Macorra, Axel Doel, Peter Gaztañaga, Enrique Gontcho, Satya Gontcho A Juneau, Stephanie Kisner, Theodore Lambert, Andrew Landriau, Martin Guillou, Laurent Le Manera, Marc Martini, Paul Meisner, Aaron Miquel, Ramon Moustakas, John Myers, Adam Poppett, Claire Prada, Francisco Rossi, Graziano Sanchez, Eusebio Schubnell, Michael Seo, Hee-Jong Sprayberry, David Tarlé, Gregory Weaver, Benjamin Alan Zou, Hu Astrophysics of Galaxies We present a study on the possible overestimation of single-epoch supermassive black hole (SMBH) masses in previous works, based on more than 55,000 type 1 quasars at $0.25 < z < 0.8$ from the Dark Energy Spectroscopic Instrument (DESI). We confirm that iron emission strength serves as a good tracer of the Eddington ratio, and estimate SMBH masses using an iron-corrected $R$-$L$ relation for H$β$, where $R$ is the broad line region size and $L$ is the continuum luminosity. Compared to our measurements, previous canonical measurements without the iron correction are overestimated by a factor of 1.5 on average. The overestimation can be up to a factor of 5 for super-Eddington quasars. The fraction of super-Eddington quasars in our sample is about 5%, significantly higher than 0.4% derived from the canonical measurements. Using a sample featuring both H$β$ and MgII emission lines, we calibrate MgII-based SMBH masses using iron-corrected, H$β$-based SMBH masses and establish an iron-corrected $R$-$L$ relation for MgII. The new relation adds an extra term of $-0.34R_{\mathrm{Fe}}$ to the $R$-$L$ relation, where $R_{\mathrm{Fe}}$ denotes the relative iron strength. We use this formula to build a catalog of about 0.5 million DESI quasars at $0.6<z<1.6$. If these iron-corrected $R$-$L$ relations for H$β$ and MgII are valid at high redshift, current mass measurements of luminous quasars at $z\ge6$ would have been overestimated by a factor of 2.3 on average, alleviating the tension between SMBH mass and growth history in the early universe. |
| title | Iron-corrected Single-epoch Black Hole Masses of DESI Quasars at low redshift |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2502.03684 |