BONATO, MATTEOMATTEOBONATOSajina, AnnaAnnaSajinaDE ZOTTI, GianfrancoGianfrancoDE ZOTTIMcKinney, JedJedMcKinneyBARONCHELLI, IVANOIVANOBARONCHELLINegrello, MattiaMattiaNegrelloMarchesini, DaniloDaniloMarchesiniRoebuck, EricEricRoebuckShipley, HeathHeathShipleyKurinsky, NoahNoahKurinskyPope, AlexandraAlexandraPopeNoriega-Crespo, AlbertoAlbertoNoriega-CrespoYan, LinLinYanKirkpatrick, AllisonAllisonKirkpatrick2021-02-092021-02-0920170004-637Xhttp://hdl.handle.net/20.500.12386/30250The James Webb Space Telescope’s Medium Resolution Spectrometer (MRS), will offer nearly two orders of magnitude improvement in sensitivity and >3× improvement in spectral resolution over our previous space-based mid-IR spectrometer, the Spitzer IRS. In this paper, we make predictions for spectroscopic pointed observations and serendipitous detections with the MRS. Specifically, pointed observations of Herschel sources require only a few minutes on source integration for detections of several star-forming and active galactic nucleus lines, out to z = 3 and beyond. But the same data will also include tens of serendipitous 0 ≲ z ≲ 4 galaxies per field with infrared luminosities ranging ∼10<SUP>6</SUP>-10<SUP>13</SUP> L <SUB>☉</SUB>. In particular, for the first time and for free we will be able to explore the L <SUB>IR</SUB> < 10<SUP>9</SUP> L <SUB>☉</SUB> regime out to z ∼ 3. We estimate that with ∼ 100 such fields, statistics of these detections will be sufficient to constrain the evolution of the low-L end of the infrared luminosity function, and hence the star formation rate function. The above conclusions hold for a wide range in the potential low-L end of the IR luminosity function, and account for the PAH deficit in low-L, low-metallicity galaxies.STAMPAenArticle10.3847/1538-4357/aa5c852-s2.0-85014449961000395919500004https://iopscience.iop.org/article/10.3847/1538-4357/aa5c852017ApJ...836..171BFIS/05 - ASTRONOMIA E ASTROFISICA