The properties of Heâ» II λ 1640 emitters at z 2.5-5 from the VANDELS survey

A. Saxena; L. Pentericci; M. Mirabelli; D. Schaerer; R. Schneider; F. Cullen; R. Amorin; M. Bolzonella; A. Bongiorno; A. C. Carnall; M. Castellano; O. Cucciati; A. Fontana; J. P.U. Fynbo; B. Garilli; A. Gargiulo; L. Guaita; N. P. Hathi; T. A. Hutchison; A. M. Koekemoer; F. Marchi; D. J. Mcleod; R. J. Mclure; C. Papovich; L. Pozzetti; M. Talia; G. Zamorani

doi:10.1051/0004-6361/201937170

The properties of Heâ» II λ 1640 emitters at z 2.5-5 from the VANDELS survey

A. Saxena, L. Pentericci, M. Mirabelli, D. Schaerer, R. Schneider, F. Cullen, R. Amorin, M. Bolzonella, A. Bongiorno, A. C. Carnall, M. Castellano, O. Cucciati, A. Fontana, J. P.U. Fynbo, B. Garilli, A. Gargiulo, L. Guaita, N. P. Hathi, T. A. Hutchison, A. M. KoekemoerF. Marchi, D. J. Mcleod, R. J. Mclure, C. Papovich, L. Pozzetti, M. Talia, G. Zamorani

Research output: Contribution to journal › Article › peer-review

48 Citations (Scopus)

Abstract

Aims. Strong Heâ» II emission is produced by low-metallicity stellar populations. Here, we aim to identify and study a sample of Heâ» IIλ1640-emitting galaxies at redshifts of zâ ∼â 2.5â -â 5 in the deep VANDELS spectroscopic survey. Methods. We identified a total of 33 Bright Heâ» II emitters (S/Nâ > â 2.5) and 17 Faint emitters (S/Nâ < â 2.5) in the VANDELS survey and used the available deep multi-wavelength data to study their physical properties. After identifying seven potential AGNs in our sample and discarding them from further analysis, we divided the sample of Bright emitters into 20 Narrow (FWHMâ < â 1000 km s^-1) and 6 Broad (FWHMâ > â 1000 km s^-1) Heâ» II emitters. We created stacks of Faint, Narrow, and Broad emitters and measured other rest-frame UV lines such as Oâ» III] and Câ» III] in both individual galaxies and stacks. We then compared the UV line ratios with the output of stellar population-synthesis models to study the ionising properties of Heâ» II emitters. Results. We do not see a significant difference between the stellar masses, star-formation rates, and rest-frame UV magnitudes of galaxies with Heâ» II and no Heâ» II emission. The stellar population models reproduce the observed UV line ratios from metals in a consistent manner, however they under-predict the total number of Heâ» II ionising photons, confirming earlier studies and suggesting that additional mechanisms capable of producing Heâ» II are needed, such as X-ray binaries or stripped stars. The models favour subsolar metallicities (∼0.1â Z_â) and young stellar ages (10⁶â -â 10⁷ years) for the Heâ» II emitters. However, the metallicity measured for Heâ» II emitters is comparable to that of non-Heâ» II emitters at similar redshifts. We argue that galaxies with Heâ» II emission may have undergone a recent star-formation event, or may be powered by additional sources of Heâ» II ionisation.

Original language	English
Article number	A47
Journal	Astronomy and Astrophysics
Volume	636
DOIs	https://doi.org/10.1051/0004-6361/201937170
Publication status	Published - 1 Apr 2020
Externally published	Yes

Keywords

Galaxies: Evolution
Galaxies: high-redshift

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.1051/0004-6361/201937170

Cite this

Saxena, A., Pentericci, L., Mirabelli, M., Schaerer, D., Schneider, R., Cullen, F., Amorin, R., Bolzonella, M., Bongiorno, A., Carnall, A. C., Castellano, M., Cucciati, O., Fontana, A., Fynbo, J. P. U., Garilli, B., Gargiulo, A., Guaita, L., Hathi, N. P., Hutchison, T. A., ... Zamorani, G. (2020). The properties of Heâ» II λ 1640 emitters at z 2.5-5 from the VANDELS survey. Astronomy and Astrophysics, 636, Article A47. https://doi.org/10.1051/0004-6361/201937170

@article{eab27034bcf14b5c865effbd69754ba3,

title = "The properties of He{\^a}» II λ 1640 emitters at z 2.5-5 from the VANDELS survey",

abstract = "Aims. Strong He{\^a}» II emission is produced by low-metallicity stellar populations. Here, we aim to identify and study a sample of He{\^a}» IIλ1640-emitting galaxies at redshifts of z{\^a} ∼{\^a} 2.5{\^a} -{\^a} 5 in the deep VANDELS spectroscopic survey. Methods. We identified a total of 33 Bright He{\^a}» II emitters (S/N{\^a} > {\^a} 2.5) and 17 Faint emitters (S/N{\^a} < {\^a} 2.5) in the VANDELS survey and used the available deep multi-wavelength data to study their physical properties. After identifying seven potential AGNs in our sample and discarding them from further analysis, we divided the sample of Bright emitters into 20 Narrow (FWHM{\^a} < {\^a} 1000 km s-1) and 6 Broad (FWHM{\^a} > {\^a} 1000 km s-1) He{\^a}» II emitters. We created stacks of Faint, Narrow, and Broad emitters and measured other rest-frame UV lines such as O{\^a}» III] and C{\^a}» III] in both individual galaxies and stacks. We then compared the UV line ratios with the output of stellar population-synthesis models to study the ionising properties of He{\^a}» II emitters. Results. We do not see a significant difference between the stellar masses, star-formation rates, and rest-frame UV magnitudes of galaxies with He{\^a}» II and no He{\^a}» II emission. The stellar population models reproduce the observed UV line ratios from metals in a consistent manner, however they under-predict the total number of He{\^a}» II ionising photons, confirming earlier studies and suggesting that additional mechanisms capable of producing He{\^a}» II are needed, such as X-ray binaries or stripped stars. The models favour subsolar metallicities (∼0.1{\^a} Z{\^a} ) and young stellar ages (106{\^a} -{\^a} 107 years) for the He{\^a}» II emitters. However, the metallicity measured for He{\^a}» II emitters is comparable to that of non-He{\^a}» II emitters at similar redshifts. We argue that galaxies with He{\^a}» II emission may have undergone a recent star-formation event, or may be powered by additional sources of He{\^a}» II ionisation.",

keywords = "Galaxies: Evolution, Galaxies: high-redshift",

author = "A. Saxena and L. Pentericci and M. Mirabelli and D. Schaerer and R. Schneider and F. Cullen and R. Amorin and M. Bolzonella and A. Bongiorno and Carnall, {A. C.} and M. Castellano and O. Cucciati and A. Fontana and Fynbo, {J. P.U.} and B. Garilli and A. Gargiulo and L. Guaita and Hathi, {N. P.} and Hutchison, {T. A.} and Koekemoer, {A. M.} and F. Marchi and Mcleod, {D. J.} and Mclure, {R. J.} and C. Papovich and L. Pozzetti and M. Talia and G. Zamorani",

note = "Publisher Copyright: {\textcopyright} ESO 2020.",

year = "2020",

month = apr,

day = "1",

doi = "10.1051/0004-6361/201937170",

language = "English",

volume = "636",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Saxena, A, Pentericci, L, Mirabelli, M, Schaerer, D, Schneider, R, Cullen, F, Amorin, R, Bolzonella, M, Bongiorno, A, Carnall, AC, Castellano, M, Cucciati, O, Fontana, A, Fynbo, JPU, Garilli, B, Gargiulo, A, Guaita, L, Hathi, NP, Hutchison, TA, Koekemoer, AM, Marchi, F, Mcleod, DJ, Mclure, RJ, Papovich, C, Pozzetti, L, Talia, M & Zamorani, G 2020, 'The properties of Heâ» II λ 1640 emitters at z 2.5-5 from the VANDELS survey', Astronomy and Astrophysics, vol. 636, A47. https://doi.org/10.1051/0004-6361/201937170

TY - JOUR

T1 - The properties of Heâ» II λ 1640 emitters at z 2.5-5 from the VANDELS survey

AU - Saxena, A.

AU - Pentericci, L.

AU - Mirabelli, M.

AU - Schaerer, D.

AU - Schneider, R.

AU - Cullen, F.

AU - Amorin, R.

AU - Bolzonella, M.

AU - Bongiorno, A.

AU - Carnall, A. C.

AU - Castellano, M.

AU - Cucciati, O.

AU - Fontana, A.

AU - Fynbo, J. P.U.

AU - Garilli, B.

AU - Gargiulo, A.

AU - Guaita, L.

AU - Hathi, N. P.

AU - Hutchison, T. A.

AU - Koekemoer, A. M.

AU - Marchi, F.

AU - Mcleod, D. J.

AU - Mclure, R. J.

AU - Papovich, C.

AU - Pozzetti, L.

AU - Talia, M.

AU - Zamorani, G.

PY - 2020/4/1

Y1 - 2020/4/1

N2 - Aims. Strong Heâ» II emission is produced by low-metallicity stellar populations. Here, we aim to identify and study a sample of Heâ» IIλ1640-emitting galaxies at redshifts of zâ ∼â 2.5â -â 5 in the deep VANDELS spectroscopic survey. Methods. We identified a total of 33 Bright Heâ» II emitters (S/Nâ > â 2.5) and 17 Faint emitters (S/Nâ < â 2.5) in the VANDELS survey and used the available deep multi-wavelength data to study their physical properties. After identifying seven potential AGNs in our sample and discarding them from further analysis, we divided the sample of Bright emitters into 20 Narrow (FWHMâ < â 1000 km s-1) and 6 Broad (FWHMâ > â 1000 km s-1) Heâ» II emitters. We created stacks of Faint, Narrow, and Broad emitters and measured other rest-frame UV lines such as Oâ» III] and Câ» III] in both individual galaxies and stacks. We then compared the UV line ratios with the output of stellar population-synthesis models to study the ionising properties of Heâ» II emitters. Results. We do not see a significant difference between the stellar masses, star-formation rates, and rest-frame UV magnitudes of galaxies with Heâ» II and no Heâ» II emission. The stellar population models reproduce the observed UV line ratios from metals in a consistent manner, however they under-predict the total number of Heâ» II ionising photons, confirming earlier studies and suggesting that additional mechanisms capable of producing Heâ» II are needed, such as X-ray binaries or stripped stars. The models favour subsolar metallicities (∼0.1â Zâ ) and young stellar ages (106â -â 107 years) for the Heâ» II emitters. However, the metallicity measured for Heâ» II emitters is comparable to that of non-Heâ» II emitters at similar redshifts. We argue that galaxies with Heâ» II emission may have undergone a recent star-formation event, or may be powered by additional sources of Heâ» II ionisation.

AB - Aims. Strong Heâ» II emission is produced by low-metallicity stellar populations. Here, we aim to identify and study a sample of Heâ» IIλ1640-emitting galaxies at redshifts of zâ ∼â 2.5â -â 5 in the deep VANDELS spectroscopic survey. Methods. We identified a total of 33 Bright Heâ» II emitters (S/Nâ > â 2.5) and 17 Faint emitters (S/Nâ < â 2.5) in the VANDELS survey and used the available deep multi-wavelength data to study their physical properties. After identifying seven potential AGNs in our sample and discarding them from further analysis, we divided the sample of Bright emitters into 20 Narrow (FWHMâ < â 1000 km s-1) and 6 Broad (FWHMâ > â 1000 km s-1) Heâ» II emitters. We created stacks of Faint, Narrow, and Broad emitters and measured other rest-frame UV lines such as Oâ» III] and Câ» III] in both individual galaxies and stacks. We then compared the UV line ratios with the output of stellar population-synthesis models to study the ionising properties of Heâ» II emitters. Results. We do not see a significant difference between the stellar masses, star-formation rates, and rest-frame UV magnitudes of galaxies with Heâ» II and no Heâ» II emission. The stellar population models reproduce the observed UV line ratios from metals in a consistent manner, however they under-predict the total number of Heâ» II ionising photons, confirming earlier studies and suggesting that additional mechanisms capable of producing Heâ» II are needed, such as X-ray binaries or stripped stars. The models favour subsolar metallicities (∼0.1â Zâ ) and young stellar ages (106â -â 107 years) for the Heâ» II emitters. However, the metallicity measured for Heâ» II emitters is comparable to that of non-Heâ» II emitters at similar redshifts. We argue that galaxies with Heâ» II emission may have undergone a recent star-formation event, or may be powered by additional sources of Heâ» II ionisation.

KW - Galaxies: Evolution

KW - Galaxies: high-redshift

UR - http://www.scopus.com/inward/record.url?scp=85083497254&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/201937170

DO - 10.1051/0004-6361/201937170

M3 - Article

AN - SCOPUS:85083497254

SN - 0004-6361

VL - 636

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A47

ER -

The properties of Heâ» II λ 1640 emitters at z 2.5-5 from the VANDELS survey

Abstract

Keywords

ASJC Scopus subject areas

Access to Document

Other files and links

Fingerprint

Cite this