{"intvolume":"       648","language":[{"iso":"eng"}],"oa_version":"Published Version","main_file_link":[{"open_access":"1","url":"https://arxiv.org/abs/1902.05960"}],"quality_controlled":"1","scopus_import":"1","title":"Exploring He II λ1640 emission line properties at z ∼2−4","keyword":["Space and Planetary Science","Astronomy and Astrophysics","galaxies: ISM / galaxies: star formation / galaxies: evolution / galaxies: high-redshift"],"date_published":"2019-04-16T00:00:00Z","year":"2019","article_type":"original","publisher":"EDP Sciences","day":"16","publication_identifier":{"issn":["0004-6361"],"eissn":["1432-0746"]},"date_updated":"2022-07-19T09:36:08Z","volume":648,"extern":"1","type":"journal_article","publication_status":"published","publication":"Astronomy & Astrophysics","article_number":"A89","abstract":[{"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.","lang":"eng"}],"_id":"11499","author":[{"last_name":"Nanayakkara","first_name":"Themiya","full_name":"Nanayakkara, Themiya"},{"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"},{"last_name":"Cantalupo","full_name":"Cantalupo, Sebastiano","first_name":"Sebastiano"},{"full_name":"Feltre, Anna","first_name":"Anna","last_name":"Feltre"},{"last_name":"Kollatschny","first_name":"Wolfram","full_name":"Kollatschny, Wolfram"},{"first_name":"Raffaella Anna","full_name":"Marino, Raffaella Anna","last_name":"Marino"},{"first_name":"Michael","full_name":"Maseda, Michael","last_name":"Maseda"},{"id":"7439a258-f3c0-11ec-9501-9df22fe06720","last_name":"Matthee","orcid":"0000-0003-2871-127X","first_name":"Jorryt J","full_name":"Matthee, Jorryt J"},{"last_name":"Paalvast","first_name":"Mieke","full_name":"Paalvast, Mieke"},{"first_name":"Johan","full_name":"Richard, Johan","last_name":"Richard"},{"first_name":"Anne","full_name":"Verhamme, Anne","last_name":"Verhamme"}],"doi":"10.1051/0004-6361/201834565","related_material":{"link":[{"relation":"erratum","url":"https://doi.org/10.1051/0004-6361/201834565e"}]},"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>","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).","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.","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>.","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.","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>"},"month":"04","date_created":"2022-07-06T09:07:06Z","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_processing_charge":"No","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","oa":1,"status":"public","external_id":{"arxiv":["1902.05960"]}}