Abstract We test the relationship between UV-derived star formation rates (SFRs) and the 7.7 μ m polycyclic aromatic hydrocarbon luminosities from the integrated emission of galaxies at z ∼ 0–2. We ...utilize multiband photometry covering 0.2–160 μ m from the Hubble Space Telescope, CFHT, JWST, Spitzer, and Herschel for galaxies in the Cosmic Evolution Early Release Science (CEERS) Survey. We perform spectral energy distribution (SED) modeling of these data to measure dust-corrected far-UV (FUV) luminosities, L FUV , and UV-derived SFRs. We then fit SED models to the JWST/MIRI 7.7–21 μ m CEERS data to derive rest-frame 7.7 μ m luminosities, L 770 , using the average flux density in the rest-frame MIRI F770W bandpass. We observe a correlation between L 770 and L FUV , where log L 770 ∝ ( 1.27 ± 0.04 ) log L FUV . L 770 diverges from this relation for galaxies at lower metallicities, lower dust obscuration, and for galaxies dominated by evolved stellar populations. We derive a “single-wavelength” SFR calibration for L 770 that has a scatter from model estimated SFRs ( σ ΔSFR ) of 0.24 dex. We derive a “multiwavelength” calibration for the linear combination of the observed FUV luminosity (uncorrected for dust) and the rest-frame 7.7 μ m luminosity, which has a scatter of σ ΔSFR = 0.21 dex. The relatively small decrease in σ suggests this is near the systematic accuracy of the total SFRs using either calibration. These results demonstrate that the rest-frame 7.7 μ m emission constrained by JWST/MIRI is a tracer of the SFR for distant galaxies to this accuracy, provided the galaxies are dominated by star formation with moderate-to-high levels of attenuation and metallicity.
Abstract
We present the mid-infrared (MIR) morphologies for 64 star-forming galaxies (SFGs) at 0.2 <
z
< 2.5 with stellar mass
M
*
> 10
9
M
⊙
using James Webb Space Telescope (JWST) Mid-Infrared ...Instrument (MIRI) observations from the Cosmic Evolution Early Release Science survey. The MIRI bands span the MIR (7.7–21
μ
m), enabling us to measure the effective radii (
R
eff
) and Sérsic indexes of these SFGs at rest-frame 6.2 and 7.7
μ
m, which contains strong emission from Polycyclic aromatic hydrocarbon (PAH) features, a well-established tracer of star formation in galaxies. We define a “PAH band” as the MIRI bandpass that contains these features at the redshift of the galaxy. We then compare the galaxy morphologies in the PAH bands to those in the rest-frame near-ultraviolet (NUV) using Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS)/F435W or ACS/F606W and optical/near-IR using HST WFC3/F160W imaging from UVCANDELS and CANDELS. The
R
eff
of galaxies in the PAH band are slightly smaller (∼10%) than those in F160W for galaxies with
M
*
≳ 10
9.5
M
⊙
at
z
≤ 1.2, but the PAH band and F160W have similar fractions of light within 1 kpc. In contrast, the
R
eff
of galaxies in the NUV band are larger, with lower fractions of light within 1 kpc compared to F160W for galaxies at
z
≤ 1.2. Using the MIRI data to estimate the SFR
IR
surface density, we find that the correlation between the SFR
IR
surface density and stellar mass has a steeper slope than that of the SFR
UV
surface density and stellar mass, suggesting more massive galaxies having increasing amounts of obscured fraction of star formation in their inner regions. This paper demonstrates how the high-angular resolution data from JWST/MIRI can reveal new information about the morphology of obscured star formation.
We test the relationship between UV-derived star formation rates (SFRs) and the 7.7 \({\mu}\)m polycyclic aromatic hydrocarbon (PAH) luminosities from the integrated emission of galaxies at z ~ 0 - ...2. We utilize multi-band photometry covering 0.2 - 160 \({\mu}\)m from HST, CFHT, JWST, Spitzer, and Herschel for galaxies in the Cosmic Evolution Early Release Science (CEERS) Survey. We perform spectral energy distribution (SED) modeling of these data to measure dust-corrected far-UV (FUV) luminosities, \(L_{FUV}\), and UV-derived SFRs. We then fit SED models to the JWST/MIRI 7.7 - 21 \({\mu}\)m CEERS data to derive rest-frame 7.7 \({\mu}\)m luminosities, \(L_{770}\), using the average flux density in the rest-frame MIRI F770W bandpass. We observe a correlation between \(L_{770}\) and \(L_{FUV}\), where log \(L_{770}\) is proportional to (1.27+/-0.04) log \(L_{FUV}\). \(L_{770}\) diverges from this relation for galaxies at lower metallicities, lower dust obscuration, and for galaxies dominated by evolved stellar populations. We derive a "single-wavelength" SFR calibration for \(L_{770}\) which has a scatter from model estimated SFRs (\({{\sigma}_{{\Delta}SFR}}\)) of 0.24 dex. We derive a "multi-wavelength" calibration for the linear combination of the observed FUV luminosity (uncorrected for dust) and the rest-frame 7.7 \({\mu}\)m luminosity, which has a scatter of \({{\sigma}_{{\Delta}SFR}}\) = 0.21 dex. The relatively small decrease in \({\sigma}\) suggests this is near the systematic accuracy of the total SFRs using either calibration. These results demonstrate that the rest-frame 7.7 \({\mu}\)m emission constrained by JWST/MIRI is a tracer of the SFR for distant galaxies to this accuracy, provided the galaxies are dominated by star-formation with moderate-to-high levels of attenuation and metallicity.
We present the mid-IR (MIR) morphologies for 64 star-forming galaxies at \(0.2<z<2.5\) with stellar mass \(\rm{M_*>10^{9}~M_\odot}\) using JWST MIRI observations from the Cosmic Evolution Early ...Release Science survey (CEERS). The MIRI bands span the MIR (7.7--21~\(\mu\)m), enabling us to measure the effective radii (\(R_{\rm{eff}}\)) and S\'{e}rsic indexes of these SFGs at rest-frame 6.2 and 7.7 \(\mu\)m, which contains strong emission from Polycyclic aromatic hydrocarbon (PAH) features, a well-established tracer of star formation in galaxies. We define a ``PAH-band'' as the MIRI bandpass that contains these features at the redshift of the galaxy. We then compare the galaxy morphologies in the PAH-bands to those in rest-frame Near-UV (NUV) using HST ACS/F435W or ACS/F606W and optical/near-IR using HST WFC3/F160W imaging from UVCANDELS and CANDELS, where the NUV-band and F160W trace the profile of (unobscured) massive stars and the stellar continuum, respectively. The \(R_{\rm{eff}}\) of galaxies in the PAH-band are slightly smaller (\(\sim\)10\%) than those in F160W for galaxies with \(\rm{M_*\gtrsim10^{9.5}~M_\odot}\) at \(z\leq1.2\), but the PAH-band and F160W have a similar fractions of light within 1 kpc. In contrast, the \(R_{\rm{eff}}\) of galaxies in the NUV-band are larger, with lower fractions of light within 1 kpc compared to F160W for galaxies at \(z\leq1.2\). Using the MIRI data to estimate the \(\rm{SFR_{\rm{IR}}}\) surface density, we find the correlation between the \(\rm{SFR_{\rm{IR}}}\) surface density and stellar mass has a steeper slope than that of the \(\rm{SFR_{\rm{UV}}}\) surface density and stellar mass, suggesting more massive galaxies having increasing amounts of obscured fraction of star formation in their inner regions. This paper demonstrates how the high-angular resolution data from JWST/MIRI can reveal new information about the morphology of obscured-star formation.
Lyman Break Galaxy (LBG) candidates at z>10 are rapidly being identified in JWST/NIRCam observations. Due to the (redshifted) break produced by neutral hydrogen absorption of rest-frame UV photons, ...these sources are expected to drop out in the bluer filters while being well detected in redder filters. However, here we show that dust-enshrouded star-forming galaxies at lower redshifts (z<7) may also mimic the near-infrared (near-IR) colors of z>10 LBGs, representing potential contaminants in LBG candidate samples. First, we analyze CEERS-DSFG-1, a NIRCam dropout undetected in the F115W and F150W filters but detected at longer wavelengths. Combining the JWST data with (sub)millimeter constraints, including deep NOEMA interferometric observations, we show that this source is a dusty star-forming galaxy (DSFG) at z~5.1. We also present a tentative 2.6sigma SCUBA-2 detection at 850um around a recently identified z~16 LBG candidate in the same field and show that, if the emission is real and associated with this candidate, the available photometry is consistent with a z~5 dusty galaxy with strong nebular emission lines despite its blue near-IR colors. Further observations on this candidate are imperative to mitigate the low confidence of this tentative submillimeter emission and its positional uncertainty. Our analysis shows that robust (sub)millimeter detections of NIRCam dropout galaxies likely imply z=4-6 redshift solutions, where the observed near-IR break would be the result of a strong rest-frame optical Balmer break combined with high dust attenuation and strong nebular line emission, rather than the rest-frame UV Lyman break. This provides evidence that DSFGs may contaminate searches for ultra high-redshift LBG candidates from JWST observations.
We report the discovery of a candidate galaxy with a photo-z of z~12 in the first epoch of the JWST Cosmic Evolution Early Release Science (CEERS) Survey. Following conservative selection criteria we ...identify a source with a robust z_phot = 11.8^+0.3_-0.2 (1-sigma uncertainty) with m_F200W=27.3, and >7-sigma detections in five filters. The source is not detected at lambda < 1.4um in deep imaging from both HST and JWST, and has faint ~3-sigma detections in JWST F150W and HST F160W, which signal a Ly-alpha break near the red edge of both filters, implying z~12. This object (Maisie's Galaxy) exhibits F115W-F200W > 1.9 mag (2-sigma lower limit) with a blue continuum slope, resulting in 99.6% of the photo-z PDF favoring z > 11. All data quality images show no artifacts at the candidate's position, and independent analyses consistently find a strong preference for z > 11. Its colors are inconsistent with Galactic stars, and it is resolved (r_h = 340 +/- 14 pc). Maisie's Galaxy has log M*/Msol ~ 8.5 and is highly star-forming (log sSFR ~ -8.2 yr^-1), with a blue rest-UV color (beta ~ -2.5) indicating little dust though not extremely low metallicity. While the presence of this source is in tension with most predictions, it agrees with empirical extrapolations assuming UV luminosity functions which smoothly decline with increasing redshift. Should followup spectroscopy validate this redshift, our Universe was already aglow with galaxies less than 400 Myr after the Big Bang.
