Kavli Affiliate: James J. Bock
| First 5 Authors: Edward Zhang, Andreas L. Faisst, Brendan Crill, Hanae Inami, Thomas Lai
| Summary:
Dust is a key galaxy component together with gas, stars, and central
supermassive black holes, playing a crucial role in stellar and galaxy
evolution. Hence, it is critical to understand galaxies’ dust content and
properties across cosmic time in order to better understand how galaxies
evolve. In addition to photometric constraints on the absorption of blue light
and its re-emission at infrared (IR) wavelengths, the detailed dust grain
properties can be explored spectroscopically via Polycyclic Aromatic
Hydrocarbon (PAH) emission bands in the mid-IR. The new SPHEREx space telescope
will conduct an all-sky spectrophotometric survey of stars and galaxies at
wavelengths of 0.75-5 ${mu}$m, making it ideal for studying the widespread
presence of the 3.3 ${mu}$m PAH emission across entire galaxy populations out
to z~0.4. In the present paper, we performed realistic simulations of galaxy
spectra to investigate the capability of SPHEREx to study PAH emission in
galaxies up to z=0.4. We find that for the all-sky survey, the PAH 3.3 ${mu}$m
emission band flux can be measured to an accuracy of 30% at
log(M/$M_odot$)>9.5 and Star Formation Rate (SFR)>1 $M_odot$ yr$^{-1}$ at
z=0.1, log(M/$M_odot$)>10.5 and SFR>10 $M_odot$ yr$^{-1}$ at z=0.2-0.3, and
log(M/$M_odot$)>11 and SFR>100 $M_odot$ yr$^{-1}$ at z=0.4. In the deep
SPHEREx fields, a factor of ~10 deeper sensitivity limits can be reached.
Overall, SPHEREx will enable the measurement of the 3.3 ${mu}$m PAH band
emission in a several hundred thousand galaxies across the sky. Given that PAH
emission originates from interactions between small dust grains ("nano grains")
and ultraviolet radiation from young stars, these measurements will provide a
population study of the smallest dust grains and radiation properties in
massive galaxies in the nearby Universe.
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