---
_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'
...