| 1. |
- Perez-Gonzalez, Pablo G., et al.
(författare)
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Life beyond 30 : Probing the-20 < M (UV) <-17 Luminosity Function at 8 < z < 13 with the NIRCam Parallel Field of the MIRI Deep Survey
- 2023
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 951:1
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Tidskriftsartikel (refereegranskat)abstract
- We present the ultraviolet luminosity function and an estimate of the cosmic star formation rate density at 8 < z < 13 derived from deep NIRCam observations taken in parallel with the MIRI Deep Survey of the Hubble Ultra Deep Field (HUDF), NIRCam covering the parallel field 2. Our deep (40 hr) NIRCam observations reach an F277W magnitude of 30.8 (5 & sigma;), more than 2 mag deeper than JWST public data sets already analyzed to find high-redshift galaxies. We select a sample of 44 z > 8 galaxy candidates based on their dropout nature in the F115W and/or F150W filters, a high probability for their photometric redshifts, estimated with three different codes, being at z > 8, good fits based on & chi; (2) calculations, and predominant solutions compared to z < 8 alternatives. We find mild evolution in the luminosity function from z & SIM; 13 to z & SIM; 8, i.e., only a small increase in the average number density of & SIM;0.2 dex, while the faint-end slope and absolute magnitude of the knee remain approximately constant, with values & alpha; = - 2.2 & PLUSMN; 0.1, and M * = - 20.8 & PLUSMN; 0.2 mag. Comparing our results with the predictions of state-of-the-art galaxy evolution models, we find two main results: (1) a slower increase with time in the cosmic star formation rate density compared to a steeper rise predicted by models; (2) nearly a factor of 10 higher star formation activity concentrated in scales around 2 kpc in galaxies with stellar masses & SIM;10(8) M (& ODOT;) during the first 350 Myr of the universe, z & SIM; 12, with models matching better the luminosity density observational estimations & SIM;150 Myr later, by z & SIM; 9.
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| 2. |
- Iani, Edoardo, et al.
(författare)
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MIDIS : JWST NIRCam and MIRI Unveil the Stellar Population Properties of Lyα Emitters and Lyman-break Galaxies at z ≃ 3–7
- 2024
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 963:2
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Tidskriftsartikel (refereegranskat)abstract
- We study the stellar population properties of 182 spectroscopically confirmed (MUSE/VLT) Lyα emitters (LAEs) and 450 photometrically selected Lyman-break galaxies (LBGs) at z = 2.8–6.7 in the Hubble Extreme Deep Field. Leveraging the combined power of Hubble Space Telescope and JWST NIRCam and MIRI observations, we analyze their rest-frame UV-through-near-IR spectral energy distributions, with MIRI playing a crucial role in robustly assessing the LAEs' stellar masses and ages. Our LAEs are low-mass objects (log10(M⋆/M⊙)≃7.5) with little or no dust extinction (E(B − V) ≃ 0.1) and a blue UV continuum slope (β ≃ −2.2). While 75% of our LAEs are young (<100 Myr), the remaining 25% have significantly older stellar populations (≥100 Myr). These old LAEs are statistically more massive, less extinct, and have lower specific star formation rate than young LAEs. Besides, they populate the plane of M⋆ versus star formation rate along the main sequence of star-forming galaxies, while young LAEs populate the starburst region. The comparison between the LAEs' properties and those of a stellar-mass-matched sample of LBGs shows no statistical difference between these objects, except for the LBGs' redder UV continuum slope and marginally larger E(B − V) values. Interestingly, 48% of the LBGs have ages <10 Myr and are classified as starbursts, but lack detectable Lyα emission. This is likely due to H i resonant scattering and/or dust-selective extinction. Overall, we find that JWST observations are crucial in determining the properties of LAEs and shedding light on their comparison with LBGs.
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| 3. |
- Bosman, Sarah E. I., et al.
(författare)
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A deep search for metals near redshift 7 : the line of sight towards ULAS J1120+0641
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 470:2, s. 1919-1934
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Tidskriftsartikel (refereegranskat)abstract
- We present a search for metal absorption line systems at the highest redshifts to date using a deep (30 h) Very Large Telescope/X=Shooter spectrum of the z = 7.084 quasi-stellar object (QSO) ULAS J1120+0641. We detect seven intervening systems at z > 5.5, with the highest redshift system being a C IV absorber at z = 6.51. We find tentative evidence that the mass density of C IV remains flat or declines with redshift at z < 6, while the number density of C II systems remains relatively flat over 5 < z < 7. These trends are broadly consistent with models of chemical enrichment by star formation-driven winds that include a softening of the ultraviolet background towards higher redshifts. We find a larger number of weak (W-rest < 0.3 angstrom) Mg II systems over 5.9 < z < 7.0 than predicted by a power-law fit to the number density of stronger systems. This is consistent with trends in the number density of weak Mg II systems at z less than or similar to 2.5, and suggests that the mechanisms that create these absorbers are already in place at z similar to 7. Finally, we investigate the associated narrow Si IV, C IV and N V absorbers located near the QSO redshift, and find that at least one component shows evidence of partial covering of the continuum source.
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| 4. |
- Zhu, Yongda, et al.
(författare)
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Probing Ultralate Reionization: Direct Measurements of the Mean Free Path over 5 z
- 2023
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 955:2
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Tidskriftsartikel (refereegranskat)abstract
- The mean free path of ionizing photons, lambda(mfp), is a critical parameter for modeling the intergalactic medium (IGM) both during and after reionization. We present direct measurements of lambda(mfp) from QSO spectra over the redshift range 5 < z < 6, including the first measurements at z similar or equal to 5.3 and 5.6. Our sample includes data from the XQR-30 VLT large program, as well as new Keck/ESI observations of QSOs near z similar to 5.5, for which we also acquire new [C II] 158 mu m redshifts with ALMA. By measuring the Lyman continuum transmission profile in stacked QSO spectra, we find lambda(mfp) = 9.33(-1.80)(+2.06), 5.40(-1.40)(+1.47), 3.31(-1.34)(+2.74), and 0.81(-0.48)(+0.73) pMpc at z = 5.08, 5.31, 5.65, and 5.93, respectively. Our results demonstrate that lambda(mfp) increases steadily and rapidly with time over 5 < z < 6. Notably, we find that lambda(mfp) deviates significantly from predictions based on a fully ionized and relaxed IGM as late as z = 5.3. By comparing our results to model predictions and indirect lambda(mfp) constraints based on IGM Ly alpha opacity, we find that the evolution of lambda(mfp) is consistent with scenarios wherein the IGM is still undergoing reionization and/or retains large fluctuations in the ionizing UV background well below redshift 6.
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