Medium-band Astrophysics with the Grism of NIRCam In Frontier Fields (MAGNIF): Spectroscopic Census of H<i>α</i> Luminosity Functions and Cosmic Star Formation at <i>z</i> ∼ 4.5 and 6.3
Shuqi Fu, Fengwu Sun, Linhua Jiang, Xiaojing Lin, J. M. Diego, Lukas J. Furtak, Mathilde Jauzac, Anton M. Koekemoer, Mingyu Li, Masamune Oguri, Nency Patel, Christopher N. A. Willmer, Rogier A. Windhorst, Adi Zitrin, F. E. Bauer, Chian-Chou Chen, Wenlei Chen, Cheng Cheng, Christopher J. Conselice, Daniel J. Eisenstein, Eiichi Egami, D. Espada, Xiaohui Fan, Seiji Fujimoto, Tiger Yu-Yang Hsiao, Xiangyu Jin, Kotaro Kohno, David Lagattuta, Zihao Li, Weizhe Liu, Jordi Miralda‐Escudé, Yuanhang Ning, Sandro Tacchella, Wei Leong Tee, Hideki Umehata, Feige Wang, Haojing Yan, Yongda Zhu
Abstract
Abstract We measure H α luminosity functions (LFs) at redshifts z ∼ 4.5 and 6.3 using the JWST Medium-band Astrophysics with the Grism of NIRCam In Frontier fields (MAGNIF) survey. MAGNIF obtained NIRCam grism spectra with the F360M and F480M filters in four Frontier Fields. We identify 248 H α emitters based on the grism spectra and photometric redshifts from combined Hubble Space Telescope and JWST imaging data. The numbers of the H α emitters show a large field-to-field variation, highlighting the necessity of multiple fields to mitigate cosmic variance. We calculate observed and dust-corrected H α LFs at the two redshifts. Thanks to the gravitational lensing, the measured H α LFs span three orders of magnitude in luminosity, and the faint-end luminosity reaches L H α ∼ 10 40.3 erg s −1 at z ∼ 4.5 and 10 41.5 erg s −1 at z ∼ 6.3. They correspond to star formation rates of ∼0.1 and 1.7 M ⊙ yr −1 , respectively. We conclude no or weak redshift evolution of the faint-end slope of H α LF across z ≃ 0.4–6.3, and the comparison with the faint-end slopes of UV LF indicates stochastic star formation history among low-mass H α emitters. The derived cosmic star formation rate densities are <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.05</mml:mn> <mml:msubsup> <mml:mn>8</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.006</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.008</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em"/> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo> </mml:msub> <mml:mspace width="0.25em"/> <mml:msup> <mml:mi>yr</mml:mi> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mi>Mpc</mml:mi> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> at z ∼ 4.5 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.02</mml:mn> <mml:msubsup> <mml:mn>5</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.007</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.009</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em"/> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo> </mml:msub> <mml:mspace width="0.25em"/> <mml:msup> <mml:mi>yr</mml:mi> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mi>Mpc</mml:mi> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> at z ∼ 6.3. These are approximately 2.2 times higher than previous estimates based on dust-corrected UV LFs, but consistent with recent measurements from infrared surveys. We discuss uncertainties in the H α LF measurements, including those propagated from the lens models, cosmic variance, and active galactic nucleus contribution, and we find that they have a negligible impact on the above results.