تقرير
A photo-$z$ cautionary tale: Redshift confirmation of COSBO-7 at $z=2.625$
| العنوان: | A photo-$z$ cautionary tale: Redshift confirmation of COSBO-7 at $z=2.625$ |
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| المؤلفون: | Jin, Shuowen, Sillassen, Nikolaj B., Hodge, Jacqueline, Magdis, Georgios E., Casey, Caitlin, Rizzo, Francesca, Koekemoer, Anton M., Valentino, Francesco, Kokorev, Vasily, Magnelli, Benjamin, Gobat, Raphael, Gillman, Steven, Franco, Maximilien, Faisst, Andreas, Kartaltepe, Jeyhan, Schinnerer, Eva, Toft, Sune, Algera, Hiddo S. B., Harish, Santosh, Lee, Minju, Liu, Daizhong, Shuntov, Marko, Talia, Margherita, Vijayan, Aswin |
| سنة النشر: | 2024 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics |
| الوصف: | Photometric redshifts are widely used in studies of dusty star-forming galaxies (DSFGs), but catastrophic photo-$z$ failure can undermine all redshift-dependent results. Here we report the spectroscopic redshift confirmation of COSBO-7, a strongly lensed DSFG in the COSMOS-PRIMER field. Recently, using 10 bands of JWST NIRCam and MIRI imaging data on COSBO-7, Ling et al. (2024) reported a photometric redshift solution of $z\gtrsim7.0$, favored by four independent spectral energy distribution (SED) fitting codes, and therefore providing an appealing candidate of the most distant massive DSFG. This photo-$z$ solution was also supported by a single line detection in ALMA Band 3 consistent with CO(7-6) at $z=7.46$. However, our new ALMA observations robustly detect two lines in Band 6 identified as CO(7-6) and [CI](2-1) at $z_{\rm spec}=2.625$, and thus the Band 3 line as CO(3-2). The three robust line detections decidedly place COSBO-7 at $z=2.625$, refuting the photo-$z$ solution. We derive physical parameters by fitting NIR-to-mm photometry and lens modeling, revealing that COSBO-7 is a main-sequence galaxy. We examine possible reasons for this photo-$z$ failure and attribute it to (1) the likely underestimation of photometric uncertainty at 0.9$\mu$m, and (2) the lack of photometry at wavelengths beyond 20$\mu$m. Notably, we recover a bona-fide $z_{\rm phot}\sim 2.3$ by including the existing MIPS $24\mu$m photometry, demonstrating the critical importance of mid-infrared data for photo-$z$ robustness. This work highlights a common challenge in modeling SEDs of DSFGs, cautioning against the reliability of photometric redshifts, as well as pseudo-spectroscopic redshifts based on single line detection. Comment: Submitted to A&A Letter |
| نوع الوثيقة: | Working Paper |
| URL الوصول: | http://arxiv.org/abs/2407.07585 |
| رقم الأكسشن: | edsarx.2407.07585 |
| قاعدة البيانات: | arXiv |
| الوصف غير متاح. |