Nebular excitation in z ∼ 2 star-forming galaxies from the SINS and LUCI surveys: The influence of shocks and active galactic nuclei

Journal Article · Mon Jan 20 00:00:00 EST 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/781/1/21· OSTI ID:22348181

Newman, Sarah F.; Genzel, Reinhard ^[1]; Buschkamp, Peter; Förster Schreiber, Natascha M.; Kurk, Jaron; Rosario, David; Davies, Ric; Eisenhauer, Frank; Lutz, Dieter ^[2]; Sternberg, Amiel ^[3]; Gnat, Orly ^[4]; Mancini, Chiara; Renzini, Alvio ^[5]; Lilly, Simon J.; Carollo, C. Marcella ^[6]; Burkert, Andreas ^[7]; Cresci, Giovanni ^[8]; Genel, Shy ^[9]; Shapiro Griffin, Kristen ^[10]; Hicks, Erin K. S., ^[11] ; others, and

---

1. Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States)
2. Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstr. 1, D-85748 Garching (Germany)
3. School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)
4. Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)
5. Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, I-35122 Padova (Italy)
6. Institute of Astronomy, Department of Physics, Eidgenössische Technische Hochschule, ETH, CH-8093 Zürich (Switzerland)
7. Universitäts-Sternwarte Ludwig-Maximilians-Universität (USM), Scheinerstr. 1, D-81679 München (Germany)
8. Istituto Nazionale di Astrofisica Osservatorio di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)
9. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
10. Space Sciences Research Group, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States)
11. Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States)

Based on high-resolution, spatially resolved data of 10 z ∼ 2 star-forming galaxies from the SINS/zC-SINF survey and LUCI data for 12 additional galaxies, we probe the excitation properties of high-z galaxies and the impact of active galactic nuclei (AGNs), shocks, and photoionization. We explore how these spatially resolved line ratios can inform our interpretation of integrated emission line ratios obtained at high redshift. Many of our galaxies fall in the 'composite' region of the z ∼ 0 [N II]/Hα versus [O III]/Hβ diagnostic (BPT) diagram, between star-forming galaxies and those with AGNs. Based on our resolved measurements, we find that some of these galaxies likely host an AGN, while others appear to be affected by the presence of shocks possibly caused by an outflow or from an enhanced ionization parameter as compared with H II regions in normal, local star-forming galaxies. We find that the Mass-Excitation (MEx) diagnostic, which separates purely star-forming and AGN hosting local galaxies in the [O III]/Hβ versus stellar mass plane, does not properly separate z ∼ 2 galaxies classified according to the BPT diagram. However, if we shift the galaxies based on the offset between the local and z ∼ 2 mass-metallicity relation (i.e., to the mass they would have at z ∼ 0 with the same metallicity), we find better agreement between the MEx and BPT diagnostics. Finally, we find that metallicity calibrations based on [N II]/Hα are more biased by shocks and AGNs at high-z than the [O III]/Hβ/[N II]/Hα calibration.

• OSTI ID: 22348181
• Journal Information: Astrophysical Journal, Vol. 781, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CALIBRATION
EMISSION
EVOLUTION
EXCITATION
GALAXY NUCLEI
MASS
METALLICITY
MILKY WAY
PHOTOIONIZATION
RED SHIFT
RESOLUTION
STARS