%0 Generic %1 saxena2019properties %A Saxena, A. %A Pentericci, L. %A Mirabelli, M. %A Schaerer, D. %A Schneider, R. %A Cullen, F. %A Amorin, R. %A Bolzonella, M. %A Bongiorno, A. %A Carnall, A. C. %A Castellano, M. %A Cucciati, O. %A Fontana, A. %A Fynbo, J. P. U. %A Garilli, B. %A Gargiulo, A. %A Guaita, L. %A Hathi, N. P. %A Hutchison, T. A. %A Marchi, F. %A McLeod, D. J. %A McLure, R. J. %A Papovich, C. %A Pozzetti, L. %A Talia, M. %A Zamorani, G. %D 2019 %K library %T The properties of He II 1640 emitters at z ~ 2.5-5 from the VANDELS survey %U http://arxiv.org/abs/1911.09999 %X Strong He II emission is produced by low-metallicity stellar populations and in this study, we aim to identify and study a sample of He II 1640 emitting galaxies at redshifts of z~2.5-5 in the deep VANDELS spectroscopic survey. We identify a total of 33 Bright He II emitters (SNR>2.5) and 17 Faint emitters (SNR<2.5) in the VANDELS survey. We use the available deep multiwavelength data to study their physical properties. After identifying 7 potential AGN in our sample and discarding them from further analysis, we divide the sample of Bright emitters into 20 Narrow (FWHM < 1000 km/s) and 6 Broad (FWHM > 1000 km/s) He II emitters. We create stacks of Faint, Narrow and Broad emitters and measure other rest-frame UV lines such as O III and C III in both individual galaxies and stacks. We then compare the UV line ratios with the output of stellar population synthesis models to study the ionising properties of He II emitters. We do not see a significant difference between the stellar masses, star-formation rates and rest-frame UV magnitudes of galaxies with He II and no He 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 II ionising photons, confirming earlier studies and suggesting that additional mechanisms capable of producing He II, such as X-ray binaries or stripped stars are needed. The models favour sub-solar metallicites (0.1 Z_sun) and young stellar ages (10^6 - 10^7 years) for the He II emitters. However, the metallicity measured for He II emitters is comparable to that of non He II emitters at similar redshifts. We argue that galaxies with He II emission may have undergone a recent star-formation event, or may be powered by additional sources of He II ionisation.

@misc{saxena2019properties, abstract = {Strong He II emission is produced by low-metallicity stellar populations and in this study, we aim to identify and study a sample of He II 1640 emitting galaxies at redshifts of z~2.5-5 in the deep VANDELS spectroscopic survey. We identify a total of 33 Bright He II emitters (SNR>2.5) and 17 Faint emitters (SNR<2.5) in the VANDELS survey. We use the available deep multiwavelength data to study their physical properties. After identifying 7 potential AGN in our sample and discarding them from further analysis, we divide the sample of Bright emitters into 20 Narrow (FWHM < 1000 km/s) and 6 Broad (FWHM > 1000 km/s) He II emitters. We create stacks of Faint, Narrow and Broad emitters and measure other rest-frame UV lines such as O III] and C III] in both individual galaxies and stacks. We then compare the UV line ratios with the output of stellar population synthesis models to study the ionising properties of He II emitters. We do not see a significant difference between the stellar masses, star-formation rates and rest-frame UV magnitudes of galaxies with He II and no He 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 II ionising photons, confirming earlier studies and suggesting that additional mechanisms capable of producing He II, such as X-ray binaries or stripped stars are needed. The models favour sub-solar metallicites (0.1 Z_sun) and young stellar ages (10^6 - 10^7 years) for the He II emitters. However, the metallicity measured for He II emitters is comparable to that of non He II emitters at similar redshifts. We argue that galaxies with He II emission may have undergone a recent star-formation event, or may be powered by additional sources of He II ionisation.}, added-at = {2019-11-25T09:24:16.000+0100}, author = {Saxena, A. and Pentericci, L. and Mirabelli, M. and Schaerer, D. and Schneider, R. and Cullen, F. and Amorin, R. and Bolzonella, M. and Bongiorno, A. and Carnall, A. C. and Castellano, M. and Cucciati, O. and Fontana, A. and Fynbo, J. P. U. and Garilli, B. and Gargiulo, A. and Guaita, L. and Hathi, N. P. and Hutchison, T. A. and Marchi, F. and McLeod, D. J. and McLure, R. J. and Papovich, C. and Pozzetti, L. and Talia, M. and Zamorani, G.}, biburl = {https://www.bibsonomy.org/bibtex/2be3c5b8b674f4fe017d92caa8838a152/gpkulkarni}, description = {The properties of He II 1640 emitters at z ~ 2.5-5 from the VANDELS survey}, interhash = {6ba3aafc90efa9988488f521c1322e3a}, intrahash = {be3c5b8b674f4fe017d92caa8838a152}, keywords = {library}, note = {cite arxiv:1911.09999Comment: 19 pages, 10 figures (including appendix), submitted to A&A. Comments welcome!}, timestamp = {2019-11-25T09:24:16.000+0100}, title = {The properties of He II 1640 emitters at z ~ 2.5-5 from the VANDELS survey}, url = {http://arxiv.org/abs/1911.09999}, year = 2019 }