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| 2. |
- Rinaldi, P., et al.
(författare)
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MIDIS : Strong (H beta plus [OIII]) and Ha Emitters at Redshift z similar or equal to 7-8 Unveiled with JWST NIRCam and MIRI Imaging in the Hubble eXtreme Deep Field
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 952:2
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Tidskriftsartikel (refereegranskat)abstract
- We make use of JWST medium-band and broadband NIRCam imaging, along with ultradeep MIRI 5.6 mu m imaging, in the Hubble eXtreme Deep Field to identify prominent line emitters at z similar or equal to 7-8. Out of a total of 58 galaxies at z similar or equal to 7-8, we find 18 robust candidates ( similar or equal to 31%) for (H beta + [O III]) emitters, based on their enhanced fluxes in the F430M and F444W filters, with EW0(H beta +[O III]) similar or equal to 87-2100 angstrom. Among these emitters, 16 lie in the MIRI coverage area and 12 exhibit a clear flux excess at 5.6 mu m, indicating the simultaneous presence of a prominent Ha emission line with EW0(H alpha) similar or equal to 200-3000 angstrom. This is the first time that H alpha emission can be detected in individual galaxies at z > 7. The Ha line, when present, allows us to separate the contributions of H beta and [O III] to the (H beta +[O III]) complex and derive Ha-based star formation rates (SFRs). We find that in most cases [O III]/ H beta > 1. Instead, two galaxies have [O III]/H beta < 1, indicating that the NIRCam flux excess is mainly driven by H beta. Most prominent line emitters are very young starbursts or galaxies on their way to/from the starburst cloud. They make for a cosmic SFR density log(10)( rho(SFRH alpha) (M-circle dot yr(-1) Mpc))similar or equal to - 2.351 3 which is about a quarter of the total value (log(10)( SFR (M-circle dot yr(-1) Mpc))similar or equal to - 1.761 3 ) at z similar or equal to 7-8. Therefore, the strong Ha emitters likely had a significant role in reionization.
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| 5. |
- Colina, L., et al.
(författare)
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Uncovering the stellar structure of the dusty star-forming galaxy GN20 at z=4.055 with MIRI/JWST
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 673
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Tidskriftsartikel (refereegranskat)abstract
- Luminous infrared galaxies at high redshifts (z > 4) include extreme starbursts that build their stellar mass over short periods of time, that is, of 100 Myr or less. These galaxies are considered to be the progenitors of massive quiescent galaxies at intermediate redshifts (z similar to 2) but their stellar structure and buildup is unknown. Here, we present the first spatially resolved near-infrared (rest-frame 1.1 mu m) imaging of GN20, one of the most luminous dusty star-forming galaxies known to date, observed at an epoch when the Universe was only 1.5 Gyr old. The 5.6 mu m image taken with the JWST Mid-Infrared Instrument (MIRI/JWST) shows that GN20 is a very luminous galaxy (M-1.1 mu m,M- AB = 25.01, uncorrected for internal extinction), with a stellar structure composed of a conspicuous central source and an extended envelope. The central source is an unresolved nucleus that carries 9% of the total flux. The nucleus is co-aligned with the peak of the cold dust emission, and offset by 3.9 kpc from the ultraviolet stellar emission. The diffuse stellar envelope is similar in size (3.6 kpc effective radius) to the clumpy CO molecular gas distribution. The centroid of the stellar envelope is offset by 1 kpc from the unresolved nucleus, suggesting GN20 is involved in an interaction or merger event supported by its location as the brightest galaxy in a proto-cluster. Additional faint stellar clumps appear to be associated with some of the UV- and CO-clumps. The stellar size of GN20 is larger by a factor of about 3 to 5 than known spheroids, disks, and irregulars at z similar to 4, while its size and low Sersic index are similar to those measured in dusty, infrared luminous galaxies at redshift 2 of the same mass (similar to 10(11) M-circle dot). GN20 has all the ingredients necessary for evolving into a massive spheroidal quiescent galaxy at intermediate redshift: it is a large, luminous galaxy at z = 4.05 involved in a short and massive starburst centred in the stellar nucleus and extended over the entire galaxy, out to radii of 4 kpc, and likely induced by the interaction or merger with a member of the proto-cluster.
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| 6. |
- Heintz, K. E., et al.
(författare)
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The Gas and Stellar Content of a Metal-poor Galaxy at z = 8.496 as Revealed by JWST and ALMA
- 2023
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 944:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a joint analysis of the galaxy S04590 at z = 8.496 based on NIRSpec, NIRCam, and NIRISS observations obtained as part of the Early Release Observations program of the James Webb Space Telescope (JWST) and the far-infrared [C ii] 158 μm emission line detected by dedicated Atacama Large Millimeter/submillimeter Array (ALMA) observations. We determine the physical properties of S04590 from modeling of the spectral energy distribution (SED) and through the redshifted optical nebular emission lines detected with JWST/NIRSpec. The best-fit SED model reveals a low-mass (M ⋆ = 107.2-108 M ⊙) galaxy with a low oxygen abundance of 12 + log ( O / H ) = 7.16 − 0.12 + 0.10 derived from the strong nebular and auroral emission lines. Assuming that [C ii] effectively traces the interstellar medium, we estimate the total gas mass of the galaxy to be M gas = (8.0 ± 4.0) × 108 M ⊙ based on the luminosity and spatial extent of [C ii]. This yields an exceptionally high gas fraction, f gas = M gas/(M gas + M ⋆) ≳ 90%, though one still consistent with the range expected for low metallicity. We further derive the metal mass of the galaxy based on the gas mass and gas-phase metallicity, which we find to be consistent with the expected metal production from Type II supernovae. Finally, we make the first constraints on the dust-to-gas (DTG) and dust-to-metal (DTM) ratios of galaxies in the epoch of reionization at z ≳ 6, showing overall low mass ratios of logDTG < −3.8 and logDTM < −0.5, though they are consistent with established scaling relations and in particular with those of the local metal-poor galaxy I Zwicky 18. Our analysis highlights the synergy between ALMA and JWST in characterizing the gas, metal, and stellar content of the first generation of galaxies.
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| 7. |
- Melin, Jeanette, et al.
(författare)
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Traceability and comparability through crosswalks with the NeuroMET Memory Metric
- 2023
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Ingår i: Scientific Reports. - : Nature Research. - 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Accurate assessment of memory ability for persons on the continuum of Alzheimer’s disease (AD) is vital for early diagnosis, monitoring of disease progression and evaluation of new therapies. However, currently available neuropsychological tests suffer from a lack of standardization and metrological quality assurance. Improved metrics of memory can be created by carefully combining selected items from legacy short-term memory tests, whilst at the same time retaining validity, and reducing patient burden. In psychometrics, this is known as “crosswalks” to link items empirically. The aim of this paper is to link items from different types of memory tests. Memory test data were collected from the European EMPIR NeuroMET and the SmartAge studies recruited at Charité Hospital (Healthy controls n = 92; Subjective cognitive decline n = 160; Mild cognitive impairment n = 50; and AD n = 58; age range 55–87). A bank of items (n = 57) was developed based on legacy short-term memory items (i.e., Corsi Block Test, Digit Span Test, Rey’s Auditory Verbal Learning Test, Word Learning Lists from the CERAD test battery and Mini Mental State Examination; MMSE). The NeuroMET Memory Metric (NMM) is a composite metric that comprises 57 dichotomous items (right/wrong). We previously reported on a preliminary item bank to assess memory based on immediate recall, and have now demonstrated direct comparability of measurements generated from the different legacy tests. We created crosswalks between the NMM and the legacy tests and between the NMM and the full MMSE using Rasch analysis (RUMM2030) and produced two conversion tables. Measurement uncertainties for estimates of person memory ability with the NMM across the full span were smaller than all individual legacy tests, which demonstrates the added value of the NMM. Comparisons with one (MMSE) of the legacy tests showed however higher measurement uncertainties of the NMM for people with a very low memory ability (raw score ≤ 19). The conversion tables developed through crosswalks in this paper provide clinicians and researchers with a practical tool to: (i) compensate for ordinality in raw scores, (ii) ensure traceability to make reliable and valid comparisons when measuring person ability, and (iii) enable comparability between test results from different legacy tests. © 2023, The Author(s).
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| 8. |
- Puglisi, A., et al.
(författare)
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KURVS: the outer rotation curve shapes and dark matter fractions of z ∼1.5 star-forming galaxies
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 524:2, s. 2814-2835
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Tidskriftsartikel (refereegranskat)abstract
- We present first results from the KMOS Ultra-deep Rotation Velocity Survey (KURVS), aimed at studying the outer rotation curves shape and dark matter content of 22 star-forming galaxies at z ∼1.5. These galaxies represent 'typical' star-forming discs at z ∼1.5, being located within the star-forming main sequence and stellar mass-size relation with stellar masses 9.5 ≤ log(M*/M⊙) ≤ 11.5. We use the spatially resolved H α emission to extract individual rotation curves out to 4 times the effective radius, on average, or ∼10-15 kpc. Most rotation curves are flat or rising between three and six disc scale radii. Only three objects with dispersion-dominated dynamics (vrot/σ0 ∼0.2) have declining outer rotation curves at more than 5σ significance. After accounting for seeing and pressure support, the nine rotation-dominated discs with vrot/σ0 ≥ 1.5 have average dark matter fractions of at the effective radius, similar to local discs. Together with previous observations of star-forming galaxies at cosmic noon, our measurements suggest a trend of declining dark matter fraction with increasing stellar mass and stellar mass surface density at the effective radius. Measurements of simulated EAGLE galaxies are in quantitative agreement with observations up to log, and overpredict the dark matter fraction of galaxies with higher mass surface densities by a factor of ∼3. We conclude that the dynamics of typical rotationally-supported discs at z ∼1.5 is dominated by dark matter from effective radius scales, in broad agreement with cosmological models. The tension with observations at high stellar mass surface density suggests that the prescriptions for baryonic processes occurring in the most massive galaxies (such as bulge growth and quenching) need to be reassessed.
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| 9. |
- 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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| 10. |
- Johnson, GGRJ, et al.
(författare)
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A New Inexpensive Simulation Model for Ultrasound Assessment of Optic Nerve Sheath Diameter
- 2020
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Ingår i: The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques. - : Cambridge University Press (CUP). - 0317-1671 .- 2057-0155. ; 47:4, s. 543-548
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Tidskriftsartikel (refereegranskat)abstract
- Background:Sonographic measurement of optic nerve sheath diameter (ONSD) is becoming increasingly accepted as a diagnostic modality to detect elevations in intracranial pressure. As this technique becomes more widespread, methods to address the inherent operator-dependent nature of this modality will need to be developed. We propose a novel low-cost model to accurately simulate sonographic ONSD measurement for purposes of training and assessment.Methods:We designed models composed of medical tubing of various diameters readily available from typical hospital supplies and suspended them in gelatin. The models were evaluated by ultrasound by three expert point-of-care sonographers using a standard linear array probe and technique proposed in the literature.Results:This model generates faithful simulation of the ONS that closely approximates in vivo images and can be used to produce accurate, reproducible measurements. Materials are low cost and easy to acquire and assemble.Conclusions:Our model provides realistic simulated images of the ONS. Through comparison of sonographic measurements to the known tube diameters, this model serves as a promising inexpensive tool to teach the method of ultrasound assessment of ONSD or as a way to determine accuracy of this novel ultrasound technology.
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