---
_id: '11507'
abstract:
- lang: eng
text: 'Lyman-α (Lyα) is intrinsically the brightest line emitted from active galaxies.
While it originates from many physical processes, for star-forming galaxies the
intrinsic Lyα luminosity is a direct tracer of the Lyman-continuum (LyC) radiation
produced by the most massive O- and early-type B-stars (M⋆ ≳ 10 M⊙) with lifetimes
of a few Myrs. As such, Lyα luminosity should be an excellent instantaneous star
formation rate (SFR) indicator. However, its resonant nature and susceptibility
to dust as a rest-frame UV photon makes Lyα very hard to interpret due to the
uncertain Lyα escape fraction, fesc, Lyα. Here we explore results from the CAlibrating
LYMan-α with Hα (CALYMHA) survey at z = 2.2, follow-up of Lyα emitters (LAEs)
at z = 2.2 − 2.6 and a z ∼ 0−0.3 compilation of LAEs to directly measure fesc, Lyα
with Hα. We derive a simple empirical relation that robustly retrieves fesc, Lyα
as a function of Lyα rest-frame EW (EW0): fesc,Lyα = 0.0048 EW0[Å] ± 0.05 and
we show that it constrains a well-defined anti-correlation between ionisation
efficiency (ξion) and dust extinction in LAEs. Observed Lyα luminosities and EW0
are easy measurable quantities at high redshift, thus making our relation a practical
tool to estimate intrinsic Lyα and LyC luminosities under well controlled and
simple assumptions. Our results allow observed Lyα luminosities to be used to
compute SFRs for LAEs at z ∼ 0−2.6 within ±0.2 dex of the Hα dust corrected SFRs.
We apply our empirical SFR(Lyα,EW0) calibration to several sources at z ≥ 2.6
to find that star-forming LAEs have SFRs typically ranging from 0.1 to 20 M⊙ yr−1
and that our calibration might be even applicable for the most luminous LAEs within
the epoch of re-ionisation. Our results imply high ionisation efficiencies (log10[ξion/Hz erg−1]
= 25.4−25.6) and low dust content in LAEs across cosmic time, and will be easily
tested with future observations with JWST which can obtain Hα and Hβ measurements
for high-redshift LAEs.'
acknowledgement: We thank the anonymous referees for multiple comments and suggestions
which have improved the manuscript. JM acknowledges the support of a Huygens PhD
fellowship from Leiden University. We have benefited greatly from the publicly available
programming language PYTHON, including the NUMPY & SCIPY (Van Der Walt et al. 2011;
Jones et al. 2001), MATPLOTLIB (Hunter 2007) and ASTROPY (Astropy Collaboration
2013) packages, and the TOPCAT analysis program (Taylor 2013). The results and samples
of LAEs used for this paper are publicly available (see e.g. Sobral et al. 2017,
2018a) and we also provide the toy model used as a PYTHON script.
article_number: A157
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: David
full_name: Sobral, David
last_name: Sobral
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
citation:
ama: 'Sobral D, Matthee JJ. Predicting Lyα escape fractions with a simple observable:
Lyα in emission as an empirically calibrated star formation rate indicator. Astronomy
& Astrophysics. 2019;623. doi:10.1051/0004-6361/201833075'
apa: 'Sobral, D., & Matthee, J. J. (2019). Predicting Lyα escape fractions with
a simple observable: Lyα in emission as an empirically calibrated star formation
rate indicator. Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/201833075'
chicago: 'Sobral, David, and Jorryt J Matthee. “Predicting Lyα Escape Fractions
with a Simple Observable: Lyα in Emission as an Empirically Calibrated Star Formation
Rate Indicator.” Astronomy & Astrophysics. EDP Sciences, 2019. https://doi.org/10.1051/0004-6361/201833075.'
ieee: 'D. Sobral and J. J. Matthee, “Predicting Lyα escape fractions with a simple
observable: Lyα in emission as an empirically calibrated star formation rate indicator,”
Astronomy & Astrophysics, vol. 623. EDP Sciences, 2019.'
ista: 'Sobral D, Matthee JJ. 2019. Predicting Lyα escape fractions with a simple
observable: Lyα in emission as an empirically calibrated star formation rate indicator.
Astronomy & Astrophysics. 623, A157.'
mla: 'Sobral, David, and Jorryt J. Matthee. “Predicting Lyα Escape Fractions with
a Simple Observable: Lyα in Emission as an Empirically Calibrated Star Formation
Rate Indicator.” Astronomy & Astrophysics, vol. 623, A157, EDP Sciences,
2019, doi:10.1051/0004-6361/201833075.'
short: D. Sobral, J.J. Matthee, Astronomy & Astrophysics 623 (2019).
date_created: 2022-07-06T11:08:16Z
date_published: 2019-03-26T00:00:00Z
date_updated: 2022-07-19T09:37:20Z
day: '26'
doi: 10.1051/0004-6361/201833075
extern: '1'
external_id:
arxiv:
- '1803.08923'
intvolume: ' 623'
keyword:
- Space and Planetary Science
- Astronomy and Astrophysics
- 'galaxies: high-redshift / galaxies: star formation / galaxies: statistics / galaxies:
evolution / galaxies: formation / galaxies: ISM'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://arxiv.org/abs/1803.08923
month: '03'
oa: 1
oa_version: Published Version
publication: Astronomy & Astrophysics
publication_identifier:
eissn:
- 1432-0746
issn:
- 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'Predicting Lyα escape fractions with a simple observable: Lyα in emission
as an empirically calibrated star formation rate indicator'
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 623
year: '2019'
...
---
_id: '11558'
abstract:
- lang: eng
text: We present and explore deep narrow- and medium-band data obtained with the
Subaru and the Isaac Newton Telescopes in the ∼2 deg2 COSMOS field. We use these
data as an extremely wide, low-resolution (R ∼ 20–80) Integral Field Unit survey
to slice through the COSMOS field and obtain a large sample of ∼4000 Ly α emitters
(LAEs) from z ∼ 2 to 6 in 16 redshift slices (SC4K). We present new Ly α luminosity
functions (LFs) covering a comoving volume of ∼108 Mpc3. SC4K extensively complements
ultradeep surveys, jointly covering over 4 dex in Ly α luminosity and revealing
a global (2.5 < z < 6) synergy LF with α=−1.93+0.12−0.12, log10Φ∗Lyα=−3.45+0.22−0.29 Mpc−3,
and log10L∗Lyα=42.93+0.15−0.11 erg s−1. The Schechter component of the Ly α LF
reveals a factor ∼5 rise in L∗Lyα and a ∼7 × decline in Φ∗Lyα from z ∼ 2 to 6.
The data reveal an extra power-law (or Schechter) component above LLy α ≈ 1043.3 erg s−1
at z ∼ 2.2–3.5 and we show that it is partially driven by X-ray and radio active
galactic nucleus (AGN), as their Ly α LF resembles the excess. The power-law component
vanishes and/or is below our detection limits above z > 3.5, likely linked with
the evolution of the AGN population. The Ly α luminosity density rises by a factor
∼2 from z ∼ 2 to 3 but is then found to be roughly constant (1.1+0.2−0.2×1040 erg s−1 Mpc−3)
to z ∼ 6, despite the ∼0.7 dex drop in ultraviolet (UV) luminosity density. The
Ly α/UV luminosity density ratio rises from 4 ± 1 per cent to 30 ± 6 per cent
from z ∼ 2.2 to 6. Our results imply a rise of a factor of ≈2 in the global ionization
efficiency (ξion) and a factor ≈4 ± 1 in the Ly α escape fraction from z ∼ 2 to
6, hinting for evolution in both the typical burstiness/stellar populations and
even more so in the typical interstellar medium conditions allowing Ly α photons
to escape.
acknowledgement: "We thank the anonymous referee for their constructive comments that
helped us improve the manuscript. DS acknowledges the hospitality of the IAC and
a Severo Ochoa visiting grant. SS and JC acknowledge studentships from the Lancaster
University. JM acknowledges a Huygens PhD fellowship from Leiden University. APA
acknowledges financial support from the Science and Technology Foundation (FCT,
Portugal) through research grants UID/FIS/04434/2013 and fellowship PD/BD/52706/2014.
The authors thank Alyssa Drake, Kimihiko Nakajima, Yuichi Harikane, Max Gronke,
Irene Shivaei, Helmut Dannerbauer, Huub Rottgering, ¨ Marius Eide, and Masami Ouchi
for many engaging and stimulating discussions. We also thank Sara Perez, Alex Bennett,
and Tom Rose for their involvement in the early stages of this project. Based on
data products from observations made with European Southern Observatory (ESO) Telescopes
at the La Silla Paranal Observatory under ESO programme IDs 294.A-5018, 097.A 0943,\r\n098.A-0819,
099.A-0254, and 179.A-2005 and on data products produced by TERAPIX and the Cambridge
Astronomy Survey Unit on behalf of the UltraVISTA consortium. Based on observations
using the WFC on the 2.5 m INT, as part of programmes 2013AN002, 2013BN008, 2014AC88,
2014AN002, 2014BN006, 2014BC118, and 2016AN001. The INT is operated on the island
of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los
Muchachos of the Instituto de Astrofisica de Canarias. This work is based in part
on data products produced at TERAPIX available at the Canadian Astronomy Data Centre
as part of the Canada–France– Hawaii Telescope Legacy Survey (CFHTLS), a collaborative
project of NRC and CNRS.\r\nWe are grateful to the CFHTLS, COSMOS-UltraVISTA, and
COSMOS survey teams. We are also unmeasurably thankful to the pioneering and continuous
work from previous Ly α surveys’ teams. Without these previous Ly α and the wider
reach legacy surveys, this research would have been impossible. We also thank the
VUDS team for making available spectroscopic redshifts from data obtained with VIMOS
at the European Southern Observatory Very Large Telescope, Paranal, Chile, under
Large Programme 185.A-0791. Finally, the authors acknowledge the unique value of
the publicly available programming language PYTHON, including the NUMPY and SCIPY
(Van Der Walt, Colbert & Varoquaux 2011; Jones et al. 2001), MATPLOTLIB (Hunter
2007), ASTROPY (Astropy Collaboration et al. 2013), and the TOPCAT analysis program
(Taylor 2005). We publicly release a catalogue with all LAEs used in this paper
(SC4K), so it can be freely explored by the community (see five example entries
in Table A1)."
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: David
full_name: Sobral, David
last_name: Sobral
- first_name: Sérgio
full_name: Santos, Sérgio
last_name: Santos
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Ana
full_name: Paulino-Afonso, Ana
last_name: Paulino-Afonso
- first_name: Bruno
full_name: Ribeiro, Bruno
last_name: Ribeiro
- first_name: João
full_name: Calhau, João
last_name: Calhau
- first_name: Ali A
full_name: Khostovan, Ali A
last_name: Khostovan
citation:
ama: 'Sobral D, Santos S, Matthee JJ, et al. Slicing COSMOS with SC4K: The evolution
of typical Ly α emitters and the Ly α escape fraction from z ∼ 2 to 6. Monthly
Notices of the Royal Astronomical Society. 2018;476(4):4725-4752. doi:10.1093/mnras/sty378'
apa: 'Sobral, D., Santos, S., Matthee, J. J., Paulino-Afonso, A., Ribeiro, B., Calhau,
J., & Khostovan, A. A. (2018). Slicing COSMOS with SC4K: The evolution of
typical Ly α emitters and the Ly α escape fraction from z ∼ 2 to 6. Monthly
Notices of the Royal Astronomical Society. Oxford University Press. https://doi.org/10.1093/mnras/sty378'
chicago: 'Sobral, David, Sérgio Santos, Jorryt J Matthee, Ana Paulino-Afonso, Bruno
Ribeiro, João Calhau, and Ali A Khostovan. “Slicing COSMOS with SC4K: The Evolution
of Typical Ly α Emitters and the Ly α Escape Fraction from z ∼ 2 to 6.” Monthly
Notices of the Royal Astronomical Society. Oxford University Press, 2018.
https://doi.org/10.1093/mnras/sty378.'
ieee: 'D. Sobral et al., “Slicing COSMOS with SC4K: The evolution of typical
Ly α emitters and the Ly α escape fraction from z ∼ 2 to 6,” Monthly Notices
of the Royal Astronomical Society, vol. 476, no. 4. Oxford University Press,
pp. 4725–4752, 2018.'
ista: 'Sobral D, Santos S, Matthee JJ, Paulino-Afonso A, Ribeiro B, Calhau J, Khostovan
AA. 2018. Slicing COSMOS with SC4K: The evolution of typical Ly α emitters and
the Ly α escape fraction from z ∼ 2 to 6. Monthly Notices of the Royal Astronomical
Society. 476(4), 4725–4752.'
mla: 'Sobral, David, et al. “Slicing COSMOS with SC4K: The Evolution of Typical
Ly α Emitters and the Ly α Escape Fraction from z ∼ 2 to 6.” Monthly Notices
of the Royal Astronomical Society, vol. 476, no. 4, Oxford University Press,
2018, pp. 4725–52, doi:10.1093/mnras/sty378.'
short: D. Sobral, S. Santos, J.J. Matthee, A. Paulino-Afonso, B. Ribeiro, J. Calhau,
A.A. Khostovan, Monthly Notices of the Royal Astronomical Society 476 (2018) 4725–4752.
date_created: 2022-07-12T10:41:08Z
date_published: 2018-06-01T00:00:00Z
date_updated: 2022-08-19T07:04:45Z
day: '01'
doi: 10.1093/mnras/sty378
extern: '1'
external_id:
arxiv:
- '1712.04451'
intvolume: ' 476'
issue: '4'
keyword:
- Space and Planetary Science
- Astronomy and Astrophysics
- 'galaxies: evolution'
- 'galaxies: formation'
- 'galaxies: high-redshift'
- 'galaxies: luminosity function'
- mass function
- 'galaxies: statistics'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://arxiv.org/abs/1712.04451
month: '06'
oa: 1
oa_version: Preprint
page: 4725-4752
publication: Monthly Notices of the Royal Astronomical Society
publication_identifier:
eissn:
- 1365-2966
issn:
- 0035-8711
publication_status: published
publisher: Oxford University Press
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'Slicing COSMOS with SC4K: The evolution of typical Ly α emitters and the Ly α
escape fraction from z ∼ 2 to 6'
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 476
year: '2018'
...
---
_id: '11562'
abstract:
- lang: eng
text: We present the CAlibrating LYMan-α with Hα (CALYMHA) pilot survey and new
results on Lyman α (Lyα) selected galaxies at z ∼ 2. We use a custom-built Lyα
narrow-band filter at the Isaac Newton Telescope, designed to provide a matched
volume coverage to the z = 2.23 Hα HiZELS survey. Here, we present the first results
for the COSMOS and UDS fields. Our survey currently reaches a 3σ line flux limit
of ∼4 × 10−17 erg s−1 cm−2, and a Lyα luminosity limit of ∼1042.3 erg s−1. We
find 188 Lyα emitters over 7.3 × 105 Mpc3, but also find significant numbers of
other line-emitting sources corresponding to He II, C III] and C IV emission lines.
These sources are important contaminants, and we carefully remove them, unlike
most previous studies. We find that the Lyα luminosity function at z = 2.23 is
very well described by a Schechter function up to LLy α ≈ 1043 erg s−1 with L∗=1042.59+0.16−0.08
erg s−1, ϕ∗=10−3.09+0.14−0.34 Mpc−3 and α = −1.75 ± 0.25. Above LLy α ≈ 1043 erg
s−1, the Lyα luminosity function becomes power-law like, driven by X-ray AGN.
We find that Lyα-selected emitters have a high escape fraction of 37 ± 7 per cent,
anticorrelated with Lyα luminosity and correlated with Lyα equivalent width. Lyα
emitters have ubiquitous large (≈40 kpc) Lyα haloes, ∼2 times larger than their
Hα extents. By directly comparing our Lyα and Hα luminosity functions, we find
that the global/overall escape fraction of Lyα photons (within a 13 kpc radius)
from the full population of star-forming galaxies is 5.1 ± 0.2 per cent at the
peak of the star formation history. An extra 3.3 ± 0.3 per cent of Lyα photons
likely still escape, but at larger radii.
acknowledgement: 'We thank the reviewer for his/her helpful comments and suggestions
that have greatly improved this work. DS and JM acknowledge financial support from
the Netherlands Organisation for Scientific research (NWO) through a Veni fellowship.
DS also acknowledges funding from FCT through an FCT Investigator Starting Grant
and Start-up Grant (IF/01154/2012/CP0189/CT0010). PNB is grateful for support from
the UK STFC via grant ST/M001229/1. IRS acknowledges support from STFC (ST/L00075X/1),
the ERC Advanced Investigator programme DUSTYGAL 321334 and a Royal Society/Wolfson
merit award. We thank Matthew Hayes, Ryan Trainor, Kimihiko Nakajima and Anne Verhamme
for many helpful discussions and Ana Sobral, Carolina Duarte and Miguel Domingos
for taking part in observations with the NB392 filter. We also thank Sergio Santos
for helpful comments. This research is based on observations obtained on the Isaac
Newton Telescope (INT), programs: I13AN002, I14AN002, 088-INT7/14A, I14BN006, 118-INT13/14B
& I15AN008. The authors acknowledge the award of time from programmes: I13AN002,
I14AN002, 088-INT7/14A, I14BN006, 118-INT13/14B, I15AN008 on the INT. INT is operated
on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio
del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Based on
observations made with ESO Telescopes at the La Silla Paranal Observatory under
programme ID 098.A 0819. We have benefited greatly from the publicly available programming
language PYTHON, including the NUMPY, MATPLOTLIB, PYFITS, SCIPY and ASTROPY packages,
the astronomical imaging tools SEXTRACTOR, SWARP (Bertin & Arnouts 1996; Bertin
2010), SCAMP (Bertin 2006) and TOPCAT (Taylor 2005). Dedicated to the memory of
M. L. Nicolau and M. C. Serrano.'
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: David
full_name: Sobral, David
last_name: Sobral
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Philip
full_name: Best, Philip
last_name: Best
- first_name: Andra
full_name: Stroe, Andra
last_name: Stroe
- first_name: Huub
full_name: Röttgering, Huub
last_name: Röttgering
- first_name: Iván
full_name: Oteo, Iván
last_name: Oteo
- first_name: Ian
full_name: Smail, Ian
last_name: Smail
- first_name: Leah
full_name: Morabito, Leah
last_name: Morabito
- first_name: Ana
full_name: Paulino-Afonso, Ana
last_name: Paulino-Afonso
citation:
ama: 'Sobral D, Matthee JJ, Best P, et al. The CALYMHA survey: Lyα luminosity function
and global escape fraction of Lyα photons at z = 2.23. Monthly Notices of the
Royal Astronomical Society. 2017;466(1):1242-1258. doi:10.1093/mnras/stw3090'
apa: 'Sobral, D., Matthee, J. J., Best, P., Stroe, A., Röttgering, H., Oteo, I.,
… Paulino-Afonso, A. (2017). The CALYMHA survey: Lyα luminosity function and global
escape fraction of Lyα photons at z = 2.23. Monthly Notices of the Royal Astronomical
Society. Oxford University Press. https://doi.org/10.1093/mnras/stw3090'
chicago: 'Sobral, David, Jorryt J Matthee, Philip Best, Andra Stroe, Huub Röttgering,
Iván Oteo, Ian Smail, Leah Morabito, and Ana Paulino-Afonso. “The CALYMHA Survey:
Lyα Luminosity Function and Global Escape Fraction of Lyα Photons at z = 2.23.”
Monthly Notices of the Royal Astronomical Society. Oxford University Press,
2017. https://doi.org/10.1093/mnras/stw3090.'
ieee: 'D. Sobral et al., “The CALYMHA survey: Lyα luminosity function and
global escape fraction of Lyα photons at z = 2.23,” Monthly Notices of the
Royal Astronomical Society, vol. 466, no. 1. Oxford University Press, pp.
1242–1258, 2017.'
ista: 'Sobral D, Matthee JJ, Best P, Stroe A, Röttgering H, Oteo I, Smail I, Morabito
L, Paulino-Afonso A. 2017. The CALYMHA survey: Lyα luminosity function and global
escape fraction of Lyα photons at z = 2.23. Monthly Notices of the Royal Astronomical
Society. 466(1), 1242–1258.'
mla: 'Sobral, David, et al. “The CALYMHA Survey: Lyα Luminosity Function and Global
Escape Fraction of Lyα Photons at z = 2.23.” Monthly Notices of the Royal Astronomical
Society, vol. 466, no. 1, Oxford University Press, 2017, pp. 1242–58, doi:10.1093/mnras/stw3090.'
short: D. Sobral, J.J. Matthee, P. Best, A. Stroe, H. Röttgering, I. Oteo, I. Smail,
L. Morabito, A. Paulino-Afonso, Monthly Notices of the Royal Astronomical Society
466 (2017) 1242–1258.
date_created: 2022-07-12T12:04:16Z
date_published: 2017-04-01T00:00:00Z
date_updated: 2024-10-14T11:35:37Z
day: '01'
doi: 10.1093/mnras/stw3090
extern: '1'
external_id:
arxiv:
- '1609.05897'
intvolume: ' 466'
issue: '1'
keyword:
- Space and Planetary Science
- Astronomy and Astrophysics
- 'galaxies: evolution'
- 'galaxies: haloes'
- 'galaxies: high-redshift'
- 'galaxies: luminosity function'
- mass function
- 'galaxies: statistics'
- 'cosmology: observations'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://arxiv.org/abs/1609.05897
month: '04'
oa: 1
oa_version: Preprint
page: 1242-1258
publication: Monthly Notices of the Royal Astronomical Society
publication_identifier:
eissn:
- 1365-2966
issn:
- 0035-8711
publication_status: published
publisher: Oxford University Press
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'The CALYMHA survey: Lyα luminosity function and global escape fraction of
Lyα photons at z = 2.23'
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 466
year: '2017'
...