The X-ray enhancements of radio-loud quasars at high redshift: New results at $z = 4\text{ -- }7$
Fuente:
arXiv
Salvato in:
| Autori principali: | , , , , , , |
|---|---|
| Natura: | Preprint |
| Pubblicazione: |
2024
|
| Soggetti: | |
| Accesso online: | |
| Tags: |
Aggiungi Tag
Nessun Tag, puoi essere il primo ad aggiungerne!!
|
| _version_ | 1866917599879626752 |
|---|---|
| author | Zuo, Zihao Zhu, Shifu Brandt, W. N. Garmire, Gordon P. Vito, F. Wu, Jianfeng Xue, Yongquan |
| author_facet | Zuo, Zihao Zhu, Shifu Brandt, W. N. Garmire, Gordon P. Vito, F. Wu, Jianfeng Xue, Yongquan |
| contents | Highly radio-loud quasars (HRLQs; $\log R>2.5$) at $z\gtrsim 4$ show apparent enhanced X-ray emission compared to matched HRLQs at lower redshifts, perhaps due to a redshift-dependent fractional contribution to the X-ray luminosity from inverse-Compton scattering of cosmic microwave background photons (IC/CMB). Using new {\it Chandra} observations and archival X-ray data, we investigate this phenomenon with an optically flux-limited sample of 41 HRLQs at $z = 4$--5.5 all with sensitive X-ray coverage, the largest sample utilized to date by a wide margin. X-ray enhancements are assessed using X-ray-to-optical flux ratios and spectral energy distributions. We confirm the presence of X-ray enhancements at a 4.9--5.3$σ$ significance level, finding that the median factor of enhancement is $\approx 1.8$ at our sample median redshift of $z\approx 4.4$. Under a fractional IC/CMB model, the expected enhancement at lower redshifts is modest; e.g., $\approx 4$% at $z\approx 1.5$. We also investigate a sample of seven radio-loud quasars (RLQs; $\log R>1$) at even higher redshifts of $z=5.6$--6.8, using new and archival X-ray data. These RLQs also show evidence for X-ray enhancements by a median factor of $\approx 2.7$ at a 3.7--4.9$σ$ significance level. The X-ray spectral and other properties of these $z=5.6$--6.8 RLQs, however, pose challenges for a straightforward fractional IC/CMB interpretation of their enhancements. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2402_17828 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The X-ray enhancements of radio-loud quasars at high redshift: New results at $z = 4\text{ -- }7$ Zuo, Zihao Zhu, Shifu Brandt, W. N. Garmire, Gordon P. Vito, F. Wu, Jianfeng Xue, Yongquan High Energy Astrophysical Phenomena Astrophysics of Galaxies Highly radio-loud quasars (HRLQs; $\log R>2.5$) at $z\gtrsim 4$ show apparent enhanced X-ray emission compared to matched HRLQs at lower redshifts, perhaps due to a redshift-dependent fractional contribution to the X-ray luminosity from inverse-Compton scattering of cosmic microwave background photons (IC/CMB). Using new {\it Chandra} observations and archival X-ray data, we investigate this phenomenon with an optically flux-limited sample of 41 HRLQs at $z = 4$--5.5 all with sensitive X-ray coverage, the largest sample utilized to date by a wide margin. X-ray enhancements are assessed using X-ray-to-optical flux ratios and spectral energy distributions. We confirm the presence of X-ray enhancements at a 4.9--5.3$σ$ significance level, finding that the median factor of enhancement is $\approx 1.8$ at our sample median redshift of $z\approx 4.4$. Under a fractional IC/CMB model, the expected enhancement at lower redshifts is modest; e.g., $\approx 4$% at $z\approx 1.5$. We also investigate a sample of seven radio-loud quasars (RLQs; $\log R>1$) at even higher redshifts of $z=5.6$--6.8, using new and archival X-ray data. These RLQs also show evidence for X-ray enhancements by a median factor of $\approx 2.7$ at a 3.7--4.9$σ$ significance level. The X-ray spectral and other properties of these $z=5.6$--6.8 RLQs, however, pose challenges for a straightforward fractional IC/CMB interpretation of their enhancements. |
| title | The X-ray enhancements of radio-loud quasars at high redshift: New results at $z = 4\text{ -- }7$ |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2402.17828 |