TY - JOUR
T1 - The MOSDEF survey
T2 - A comprehensive analysis of the rest-optical emission-line properties of z ∼2.3 star-forming galaxies
AU - Runco, Jordan N.
AU - Shapley, Alice E.
AU - Sanders, Ryan L.
AU - Topping, Michael W.
AU - Kriek, Mariska
AU - Reddy, Naveen A.
AU - Coil, Alison L.
AU - Mobasher, Bahram
AU - Siana, Brian
AU - Freeman, William R.
AU - Shivaei, Irene
AU - Azadi, Mojegan
AU - Price, Sedona H.
AU - Leung, Gene C.K.
AU - Fetherolf, Tara
AU - De Groot, Laura
AU - Zick, Tom
AU - Fornasini, Francesca M.
AU - Barro, Guillermo
N1 - Publisher Copyright:
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
PY - 2021/4/1
Y1 - 2021/4/1
N2 - We analyse the rest-optical emission-line spectra of z ∼2.3 star-forming galaxies in the complete MOSFIRE Deep Evolution Field (MOSDEF) survey. In investigating the origin of the well-known offset between the sequences of high-redshift and local galaxies in the [O iii]λ5008/Hβ versus [N ii]λ6585/Hα ('[N ii] BPT') diagram, we define two populations of z ∼2.3 MOSDEF galaxies. These include the high population that is offset towards higher [O iii]λ5008/Hβ and/or [N ii]λ6585/Hα with respect to the local SDSS sequence and the low population that overlaps the SDSS sequence. These two groups are also segregated within the [O iii]λ5008/Hβ versus [S ii]λλ6718,6733/Hα and the [O iii]λλ4960,5008/[O ii] λλ3727,3730 (O32) versus ([O iii]λλ4960,5008+[O ii]λλ3727,3730)/Hβ (R23) diagrams, which suggests qualitatively that star-forming regions in the more offset galaxies are characterized by harder ionizing spectra at fixed nebular oxygen abundance. We also investigate many galaxy properties of the split sample and find that the high sample is on average smaller in size and less massive, but has higher specific star formation rate (SFR) and SFR surface density values and is slightly younger compared to the low population. From Cloudy+BPASS photoionization models, we estimate that the high population has a lower stellar metallicity (i.e. harder ionizing spectrum) but slightly higher nebular metallicity and higher ionization parameter compared to the low population. While the high population is more α-enhanced (i.e. higher α/Fe) than the low population, both samples are significantly more α-enhanced compared to local star-forming galaxies with similar rest-optical line ratios. These differences must be accounted for in all high-redshift star-forming galaxies-not only those 'offset' from local excitation sequences.
AB - We analyse the rest-optical emission-line spectra of z ∼2.3 star-forming galaxies in the complete MOSFIRE Deep Evolution Field (MOSDEF) survey. In investigating the origin of the well-known offset between the sequences of high-redshift and local galaxies in the [O iii]λ5008/Hβ versus [N ii]λ6585/Hα ('[N ii] BPT') diagram, we define two populations of z ∼2.3 MOSDEF galaxies. These include the high population that is offset towards higher [O iii]λ5008/Hβ and/or [N ii]λ6585/Hα with respect to the local SDSS sequence and the low population that overlaps the SDSS sequence. These two groups are also segregated within the [O iii]λ5008/Hβ versus [S ii]λλ6718,6733/Hα and the [O iii]λλ4960,5008/[O ii] λλ3727,3730 (O32) versus ([O iii]λλ4960,5008+[O ii]λλ3727,3730)/Hβ (R23) diagrams, which suggests qualitatively that star-forming regions in the more offset galaxies are characterized by harder ionizing spectra at fixed nebular oxygen abundance. We also investigate many galaxy properties of the split sample and find that the high sample is on average smaller in size and less massive, but has higher specific star formation rate (SFR) and SFR surface density values and is slightly younger compared to the low population. From Cloudy+BPASS photoionization models, we estimate that the high population has a lower stellar metallicity (i.e. harder ionizing spectrum) but slightly higher nebular metallicity and higher ionization parameter compared to the low population. While the high population is more α-enhanced (i.e. higher α/Fe) than the low population, both samples are significantly more α-enhanced compared to local star-forming galaxies with similar rest-optical line ratios. These differences must be accounted for in all high-redshift star-forming galaxies-not only those 'offset' from local excitation sequences.
KW - galaxies: ISM
KW - galaxies: evolution
KW - galaxies: high-redshift
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U2 - 10.1093/mnras/stab119
DO - 10.1093/mnras/stab119
M3 - Article
AN - SCOPUS:85104031417
SN - 0035-8711
VL - 502
SP - 2600
EP - 2614
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -