---
_id: '11585'
abstract:
- lang: eng
  text: "Observations show that star-forming galaxies reside on a tight three-dimensional
    plane between mass, gas-phase metallicity and star formation rate (SFR), which
    can be explained by the interplay between metal-poor gas inflows, SFR and outflows.
    However, different metals are released on different time-scales, which may affect
    the slope of this relation. Here, we use central, star-forming galaxies with Mstar
    = 109.0−10.5 M\f from the EAGLE hydrodynamical simulation to examine three-dimensional
    relations between mass, SFR and chemical enrichment using absolute and relative
    C, N, O and Fe abundances. We show that the scatter is smaller when gas-phase
    α-enhancement is used rather than metallicity. A similar plane also exists for
    stellar α-enhancement, implying that present-day specific SFRs are correlated
    with long time-scale star formation histories. Between z = 0 and 1, the α-enhancement
    plane is even more insensitive to redshift than the plane using metallicity. However,
    it evolves at z > 1 due to lagging iron yields. At fixed mass, galaxies with higher
    SFRs have star formation histories shifted toward late times, are more α-enhanced
    and this α-enhancement increases with redshift as observed. These findings suggest
    that relations between physical properties inferred from observations may be affected
    by systematic variations in α-enhancements."
acknowledgement: We thank the anonymous referee for their constructive comments. JM
  acknowledges the support of a Huygens PhD fellowship from Leiden University. We
  thank Jarle Brinchmann, Rob Crain and David Sobral for discussions. We acknowledge
  the use of the Topcat software (Taylor 2013) for assisting in rapid exploration
  of multi-dimensional datasets and the use of Python and its numpy, matplotlib and
  pandas packages.
article_processing_charge: No
article_type: original
arxiv: 1
author:
- 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: Matthee JJ. Differences in galaxy colours are not just about the mass. <i>Nature
    Astronomy</i>. 2021;5:984-985. doi:<a href="https://doi.org/10.1038/s41550-021-01415-y">10.1038/s41550-021-01415-y</a>
  apa: Matthee, J. J. (2021). Differences in galaxy colours are not just about the
    mass. <i>Nature Astronomy</i>. Springer Nature. <a href="https://doi.org/10.1038/s41550-021-01415-y">https://doi.org/10.1038/s41550-021-01415-y</a>
  chicago: Matthee, Jorryt J. “Differences in Galaxy Colours Are Not Just about the
    Mass.” <i>Nature Astronomy</i>. Springer Nature, 2021. <a href="https://doi.org/10.1038/s41550-021-01415-y">https://doi.org/10.1038/s41550-021-01415-y</a>.
  ieee: J. J. Matthee, “Differences in galaxy colours are not just about the mass,”
    <i>Nature Astronomy</i>, vol. 5. Springer Nature, pp. 984–985, 2021.
  ista: Matthee JJ. 2021. Differences in galaxy colours are not just about the mass.
    Nature Astronomy. 5, 984–985.
  mla: Matthee, Jorryt J. “Differences in Galaxy Colours Are Not Just about the Mass.”
    <i>Nature Astronomy</i>, vol. 5, Springer Nature, 2021, pp. 984–85, doi:<a href="https://doi.org/10.1038/s41550-021-01415-y">10.1038/s41550-021-01415-y</a>.
  short: J.J. Matthee, Nature Astronomy 5 (2021) 984–985.
date_created: 2022-07-14T13:13:39Z
date_published: 2021-07-05T00:00:00Z
date_updated: 2022-08-19T08:37:58Z
day: '05'
doi: 10.1038/s41550-021-01415-y
extern: '1'
external_id:
  arxiv:
  - '1802.06786'
intvolume: '         5'
keyword:
- Astronomy and Astrophysics
- galaxies
- formation - galaxies
- evolution - galaxies
- star formation - galaxies
- abundances
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/1802.06786
month: '07'
oa: 1
oa_version: Preprint
page: 984-985
publication: Nature Astronomy
publication_identifier:
  eissn:
  - 2397-3366
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
scopus_import: '1'
status: public
title: Differences in galaxy colours are not just about the mass
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 5
year: '2021'
...
---
_id: '11499'
abstract:
- lang: eng
  text: Deep optical spectroscopic surveys of galaxies provide a unique opportunity
    to investigate rest-frame ultra-violet (UV) emission line properties of galaxies
    at z ∼ 2 − 4.5. Here we combine VLT/MUSE Guaranteed Time Observations of the Hubble
    Deep Field South, Ultra Deep Field, COSMOS, and several quasar fields with other
    publicly available data from VLT/VIMOS and VLT/FORS2 to construct a catalogue
    of He II λ1640 emitters at z ≳ 2. The deepest areas of our MUSE pointings reach
    a 3σ line flux limit of 3.1 × 10−19 erg s−1 cm−2. After discarding broad-line
    active galactic nuclei, we find 13 He II λ1640 detections from MUSE with a median
    MUV = −20.1 and 21 tentative He II λ1640 detections from other public surveys.
    Excluding Lyα, all except two galaxies in our sample show at least one other rest-UV
    emission line, with C III] λ1907, λ1909 being the most prominent. We use multi-wavelength
    data available in the Hubble legacy fields to derive basic galaxy properties of
    our sample through spectral energy distribution fitting techniques. Taking advantage
    of the high-quality spectra obtained by MUSE (∼10 − 30 h of exposure time per
    pointing), we use photo-ionisation models to study the rest-UV emission line diagnostics
    of the He II λ1640 emitters. Line ratios of our sample can be reproduced by moderately
    sub-solar photo-ionisation models, however, we find that including effects of
    binary stars lead to degeneracies in most free parameters. Even after considering
    extra ionising photons produced by extreme sub-solar metallicity binary stellar
    models, photo-ionisation models are unable to reproduce rest-frame He II λ1640
    equivalent widths (∼0.2 − 10 Å), thus additional mechanisms are necessary in models
    to match the observed He II λ1640 properties.
acknowledgement: 'The authors wish to thank the referee for constructive comments
  that improved the paper substantially. We thank the BPASS team for making the stellar
  population models available. We thank Elizabeth Stanway, Claus Leitherer, Daniel
  Schaerer, Jorick Vink, and Nell Byler for insightful discussions. We thank the Lorentz
  Centre and the scientific organizers of the Characterizing galaxies with spectroscopy
  with a view for JWST workshop held at the Lorentz Centre in 2017 October, which
  promoted useful discussions in the wider community. TN, JB, and RB acknowledges
  the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) top grant TOP1.16.057.
  AF acknowledges support from the ERC via an Advanced Grant under grant agreement
  no. 339659-MUSICOS. JB acknowledges support by Fundação para a Ciência e a Tecnologia
  (FCT) through national funds (UID/FIS/04434/2013) and Investigador FCT contract
  IF/01654/2014/CP1215/CT0003, and by FEDER through COMPETE2020 (POCI-01-0145-FEDER-007672).
  JR acknowledges support from the ERC Starting grant 336736 (CALENDS). This research
  made use of astropy (http://www.astropy.org) a community-developed core Python package
  for Astronomy (Astropy Collaboration 2013, 2018) and pandas (McKinney 2010). Figures
  were generated using matplotlib (Hunter 2007) and seaborn (https://seaborn.pydata.org).
  Facilities: VLT (MUSE).'
article_number: A89
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Themiya
  full_name: Nanayakkara, Themiya
  last_name: Nanayakkara
- first_name: Jarle
  full_name: Brinchmann, Jarle
  last_name: Brinchmann
- first_name: Leindert
  full_name: Boogaard, Leindert
  last_name: Boogaard
- first_name: Rychard
  full_name: Bouwens, Rychard
  last_name: Bouwens
- first_name: Sebastiano
  full_name: Cantalupo, Sebastiano
  last_name: Cantalupo
- first_name: Anna
  full_name: Feltre, Anna
  last_name: Feltre
- first_name: Wolfram
  full_name: Kollatschny, Wolfram
  last_name: Kollatschny
- first_name: Raffaella Anna
  full_name: Marino, Raffaella Anna
  last_name: Marino
- first_name: Michael
  full_name: Maseda, Michael
  last_name: Maseda
- 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: Mieke
  full_name: Paalvast, Mieke
  last_name: Paalvast
- first_name: Johan
  full_name: Richard, Johan
  last_name: Richard
- first_name: Anne
  full_name: Verhamme, Anne
  last_name: Verhamme
citation:
  ama: Nanayakkara T, Brinchmann J, Boogaard L, et al. Exploring He II λ1640 emission
    line properties at z ∼2−4. <i>Astronomy &#38; Astrophysics</i>. 2019;648. doi:<a
    href="https://doi.org/10.1051/0004-6361/201834565">10.1051/0004-6361/201834565</a>
  apa: Nanayakkara, T., Brinchmann, J., Boogaard, L., Bouwens, R., Cantalupo, S.,
    Feltre, A., … Verhamme, A. (2019). Exploring He II λ1640 emission line properties
    at z ∼2−4. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences. <a href="https://doi.org/10.1051/0004-6361/201834565">https://doi.org/10.1051/0004-6361/201834565</a>
  chicago: Nanayakkara, Themiya, Jarle Brinchmann, Leindert Boogaard, Rychard Bouwens,
    Sebastiano Cantalupo, Anna Feltre, Wolfram Kollatschny, et al. “Exploring He II Λ1640
    Emission Line Properties at z ∼2−4.” <i>Astronomy &#38; Astrophysics</i>. EDP
    Sciences, 2019. <a href="https://doi.org/10.1051/0004-6361/201834565">https://doi.org/10.1051/0004-6361/201834565</a>.
  ieee: T. Nanayakkara <i>et al.</i>, “Exploring He II λ1640 emission line properties
    at z ∼2−4,” <i>Astronomy &#38; Astrophysics</i>, vol. 648. EDP Sciences, 2019.
  ista: Nanayakkara T, Brinchmann J, Boogaard L, Bouwens R, Cantalupo S, Feltre A,
    Kollatschny W, Marino RA, Maseda M, Matthee JJ, Paalvast M, Richard J, Verhamme
    A. 2019. Exploring He II λ1640 emission line properties at z ∼2−4. Astronomy &#38;
    Astrophysics. 648, A89.
  mla: Nanayakkara, Themiya, et al. “Exploring He II Λ1640 Emission Line Properties
    at z ∼2−4.” <i>Astronomy &#38; Astrophysics</i>, vol. 648, A89, EDP Sciences,
    2019, doi:<a href="https://doi.org/10.1051/0004-6361/201834565">10.1051/0004-6361/201834565</a>.
  short: T. Nanayakkara, J. Brinchmann, L. Boogaard, R. Bouwens, S. Cantalupo, A.
    Feltre, W. Kollatschny, R.A. Marino, M. Maseda, J.J. Matthee, M. Paalvast, J.
    Richard, A. Verhamme, Astronomy &#38; Astrophysics 648 (2019).
date_created: 2022-07-06T09:07:06Z
date_published: 2019-04-16T00:00:00Z
date_updated: 2022-07-19T09:36:08Z
day: '16'
doi: 10.1051/0004-6361/201834565
extern: '1'
external_id:
  arxiv:
  - '1902.05960'
intvolume: '       648'
keyword:
- Space and Planetary Science
- Astronomy and Astrophysics
- 'galaxies: ISM / galaxies: star formation / galaxies: evolution / galaxies: high-redshift'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/1902.05960
month: '04'
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'
related_material:
  link:
  - relation: erratum
    url: https://doi.org/10.1051/0004-6361/201834565e
scopus_import: '1'
status: public
title: Exploring He II λ1640 emission line properties at z ∼2−4
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 648
year: '2019'
...
---
_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. <i>Astronomy
    &#38; Astrophysics</i>. 2019;623. doi:<a href="https://doi.org/10.1051/0004-6361/201833075">10.1051/0004-6361/201833075</a>'
  apa: 'Sobral, D., &#38; Matthee, J. J. (2019). Predicting Lyα escape fractions with
    a simple observable: Lyα in emission as an empirically calibrated star formation
    rate indicator. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences. <a href="https://doi.org/10.1051/0004-6361/201833075">https://doi.org/10.1051/0004-6361/201833075</a>'
  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.” <i>Astronomy &#38; Astrophysics</i>. EDP Sciences, 2019. <a href="https://doi.org/10.1051/0004-6361/201833075">https://doi.org/10.1051/0004-6361/201833075</a>.'
  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,”
    <i>Astronomy &#38; Astrophysics</i>, 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 &#38; 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.” <i>Astronomy &#38; Astrophysics</i>, vol. 623, A157, EDP Sciences,
    2019, doi:<a href="https://doi.org/10.1051/0004-6361/201833075">10.1051/0004-6361/201833075</a>.'
  short: D. Sobral, J.J. Matthee, Astronomy &#38; 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'
...