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- Béthermin, Matthieu, et al.
(författare)
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The ALMA-ALPINE [CII] survey: Kennicutt-Schmidt relation in four massive main-sequence galaxies at z ~ 4.5
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 680
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Tidskriftsartikel (refereegranskat)abstract
- Aims. The Kennicutt-Schmidt (KS) relation between the gas and the star formation rate (SFR) surface density (Σgas - ΣSFR) is essential to understand star formation processes in galaxies. To date, it has been measured up to z ~ 2.5 in main-sequence galaxies. In this Letter our aim is to put constraints at z ~ 4.5 using a sample of four massive main-sequence galaxies observed by ALMA at high resolution. Methods. We obtained ~0.3″-resolution [CII] and continuum maps of our objects, which we then converted into gas and obscured SFR surface density maps. In addition, we produced unobscured SFR surface density maps by convolving Hubble ancillary data in the rest-frame UV. We then derived the average ΣSFR in various Σgas bins, and estimated the uncertainties using a Monte Carlo sampling. Results. Our galaxy sample follows the KS relation measured in main-sequence galaxies at lower redshift, and is slightly lower than the predictions from simulations. Our data points probe the high end both in terms of Σgas and ΣSFR, and gas depletion timescales (285-843 Myr) remain similar to z ~ 2 objects. However, three of our objects are clearly morphologically disturbed, and we could have expected shorter gas depletion timescales (≲100 Myr) similar to merger-driven starbursts at lower redshifts. This suggests that the mechanisms triggering starbursts at high redshift may be different than in the low- and intermediate-z Universe.
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| 2. |
- Gkogkou, A., et al.
(författare)
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CONCERTO: Simulating the CO, [CII], and [CI] line emission of galaxies in a 117 deg2 field and the impact of field-to-field variance
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 670
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Tidskriftsartikel (refereegranskat)abstract
- In the submillimeter regime, spectral line scans and line intensity mapping (LIM) are new promising probes for the cold gas content and star formation rate of galaxies across cosmic time. However, both of these two measurements suffer from field-to-field variance. We study the effect of field-to-field variance on the predicted CO and [CII] power spectra from future LIM experiments such as CONCERTO, as well as on the line luminosity functions (LFs) and the cosmic molecular gas mass density that are currently derived from spectral line scans. We combined a 117 deg2 dark matter lightcone from the Uchuu cosmological simulation with the simulated infrared dusty extragalactic sky (SIDES) approach. The clustering of the dusty galaxies in the SIDES-Uchuu product is validated by reproducing the cosmic infrared background anisotropies measured by Herschel and Planck. We find that in order to constrain the CO LF with an uncertainty below 20%, we need survey sizes of at least 0.1 deg2. Furthermore, accounting for the field-to-field variance using only the Poisson variance can underestimate the total variance by up to 80%. The lower the luminosity is and the larger the survey size is, the higher the level of underestimate. At z < 3, the impact of field-to-field variance on the cosmic molecular gas density can be as high as 40% for the 4.6 arcmin2 field, but drops below 10% for areas larger than 0.2 deg2. However, at z > 3 the variance decreases more slowly with survey size and for example drops below 10% for 1 deg2 fields. Finally, we find that the CO and [CII] LIM power spectra can vary by up to 50% in 1 deg2 fields. This limits the accuracy of the constraints provided by the first 1 deg2 surveys. In addition the level of the shot noise power is always dominated by the sources that are just below the detection thresholds, which limits its potential for deriving number densities of faint [CII] emitters. We provide an analytical formula to estimate the field-to-field variance of current or future LIM experiments given their observed frequency and survey size. The underlying code to derive the field-to-field variance and the full SIDES-Uchuu products (catalogs, cubes, and maps) are publicly available.
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