分类： 天文学 >> 天文学 提交时间： 2023-02-19
Xinfeng Xu
Alaina Henry
Timothy Heckman
John Chisholm
Rui Marques-Chaves
Floriane Leclercq
Danielle A. Berg
Anne Jaskot
Daniel Schaerer
Gábor Worseck
Ricardo O. Amorín
Hakim Atek
Matthew Hayes
Zhiyuan Ji
Göran Östlin
Alberto Saldana-Lopez
Trinh Thuan
摘要： The Mg II 2796, 2803 doublet has been suggested to be a useful indirect indicator for the escape of Ly-alpha and Lyman continuum (LyC) photons in local star-forming galaxies. However, studies to date have focused on small samples of galaxies with strong Mg II or strong LyC emission. Here we present the first study of Mg II probing a large dynamic range of galaxy properties, using newly obtained high signal-to-noise, moderate-resolution spectra of Mg II for a sample of 34 galaxies selected from the Low-redshift Lyman Continuum Survey. We show that the galaxies in our sample have Mg II profiles ranging from strong emission to P-Cygni profiles, and to pure absorption. We find there is a significant trend (with a possibility of spurious correlations of ~ 2%) that galaxies detected as strong LyC Emitters (LCEs) also show larger equivalent widths of Mg II emission, and non-LCEs tend to show evidence of more scattering and absorption features in Mg II We then find Mg II strongly correlates with Ly-alpha in both equivalent width and escape fraction, regardless of whether the emission or absorption dominates the Mg II profiles. Furthermore, we present that, for galaxies categorized as Mg II emitters (MgE), one can adopt the information of Mg II, metallicity, and dust to estimate the escape fraction of LyC within a factor of 3. These findings confirm that Mg II lines can be used as a tool to select galaxies as LCEs and to serve as an indirect indicator for the escape of Ly-alpha and LyC.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Roland Bacon
Jarle Brinchmann
Simon Conseil
Michael Maseda
Themiya Nanayakkara
Martin Wendt
Raphael Bacher
David Mary
Peter M. Weilbacher
Davor Krajnovic
Leindert Boogaard
Nicolas Bouche
Thierry Contini
Benoit Epinat
Anna Feltre
Yucheng Guo
Christian Herenz
Wolfram Kollatschny
Haruka Kusakabe
Floriane Leclercq
摘要： We present the second data release of the MUSE Hubble UDF surveys, which includes the deepest spectroscopic survey ever performed. The MUSE data, with their 3D content, amazing depth, wide spectral range, and excellent spatial and medium spectral resolution, are rich in information. This update of the first release incorporates a new 141-hour adaptive-optics-assisted MXDF field (1' diameter FoV) in addition to the reprocessed 10-hour mosaic (3'x3') and the single 31-hour deep field (1'x1'). We have securely identified and measured the redshift of 2221 sources, an increase of 41% compared to the first release. With the exception of 8 stars, the collected sample consists of 25 nearby galaxies (z 3, the difference is even more striking, with a factor of 65 increase (1308 vs 20). We compared the measured redshifts against three published photometric redshift catalogs and find the photo-z accuracy to be lower than the constraints provided by photo-z fitting codes. 80% of the galaxies have an HST counterpart. They are on average faint, with a median magnitude of 25.7 and 28.7 for the OII and Ly-alpha emitters, respectively. SED fits show that these galaxies tend to be low-mass star-forming galaxies, with a median stellar mass of 6.2 10**8 M and a median SFR of 0.4 M/yr. 20% of our catalog, or 424 galaxies, have no HST counterpart. The vast majority of these new sources are high EQW z>2.8 LAEs that are detected by MUSE thanks to their bright and asymmetric broad Ly-alpha line. We release advanced data products, specific software, and a web interface to select and download data sets.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Maxime Trebitsch
Pratika Dayal
John Chisholm
Steven L. Finkelstein
Anne Jaskot
Sophia Flury
Daniel Schaerer
Hakim Atek
Sanchayeeta Borthakur
Harry Ferguson
Fabio Fontanot
Mauro Giavalisco
Andrea Grazian
Matthew Hayes
Floriane Leclercq
Göran Östlin
Alberto Saldana-Lopez
Trinh X. Thuan
Bingjie Wang
Gábor Worseck
摘要： The fraction of ionizing photons escaping from galaxies, $f_{esc}$, is at the same time a crucial parameter in modelling reionization and a very poorly known quantity, especially at high redshift. Recent observations are starting to constrain the values of $f_{esc}$ in low-z star-forming galaxies, but the validity of this comparison remains to be verified. Applying at high-z the empirical relation between $f_{esc}$ and the UV slope trends derived from the Low-z Lyman Continuum Survey, we use the DELPHI semi-analytical galaxy formation model to estimate the global ionizing emissivity of high-z galaxies, which we use to compute the resulting reionization history. We find that both the global ionizing emissivity and reionization history match the observational constraints. Assuming that the low-z correlations hold during the epoch of reionization, we find that galaxies with $-16 \lesssim M_{UV} \lesssim -13.5$ are the main drivers of reionization. We derive a population-averaged $\langle f_{esc} \rangle \simeq 8\%, 10\%, 20\%$ at z=4.5, 6, 8.
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