ORCID Profile
0000-0001-8460-1564
Current Organisation
University of Groningen
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Sensory Processes, Perception and Performance | Psychology | Behavioural Ecology |
Expanding Knowledge in the Biological Sciences | Expanding Knowledge in Psychology and Cognitive Sciences | Expanding Knowledge in Technology
Publisher: American Meteorological Society
Date: 04-0011
Abstract: Extratropical transition (ET) is the process by which a tropical cyclone, upon encountering a baroclinic environment and reduced sea surface temperature at higher latitudes, transforms into an extratropical cyclone. This process is influenced by, and influences, phenomena from the tropics to the midlatitudes and from the meso- to the planetary scales to extents that vary between in idual events. Motivated in part by recent high-impact and/or extensively observed events such as North Atlantic Hurricane Sandy in 2012 and western North Pacific Typhoon Sinlaku in 2008, this review details advances in understanding and predicting ET since the publication of an earlier review in 2003. Methods for diagnosing ET in reanalysis, observational, and model-forecast datasets are discussed. New climatologies for the eastern North Pacific and southwest Indian Oceans are presented alongside updates to western North Pacific and North Atlantic Ocean climatologies. Advances in understanding and, in some cases, modeling the direct impacts of ET-related wind, waves, and precipitation are noted. Improved understanding of structural evolution throughout the transformation stage of ET fostered in large part by novel aircraft observations collected in several recent ET events is highlighted. Predictive skill for operational and numerical model ET-related forecasts is discussed along with environmental factors influencing posttransition cyclone structure and evolution. Operational ET forecast and analysis practices and challenges are detailed. In particular, some challenges of effective hazard communication for the evolving threats posed by a tropical cyclone during and after transition are introduced. This review concludes with recommendations for future work to further improve understanding, forecasts, and hazard communication.
Publisher: Oxford University Press (OUP)
Date: 27-05-2019
Publisher: American Astronomical Society
Date: 17-02-2017
Publisher: American Astronomical Society
Date: 09-2023
Publisher: American Astronomical Society
Date: 03-08-2018
Publisher: American Astronomical Society
Date: 06-2023
Abstract: MACS0647–JD is a triply lensed z ∼ 11 galaxy originally discovered with the Hubble Space Telescope. The three lensed images are magnified by factors of ∼8, 5, and 2 to AB mag 25.1, 25.6, and 26.6 at 3.5 μ m. The brightest is over a magnitude brighter than other galaxies recently discovered at similar redshifts z 10 with JWST. Here, we report new JWST imaging that clearly resolves MACS0647–JD as having two components that are either merging galaxies or stellar complexes within a single galaxy. The brighter larger component “A” is intrinsically very blue ( β ∼ −2.6 ± 0.1), likely due to very recent star formation and no dust, and is spatially extended with an effective radius ∼70 ± 24 pc. The smaller component “B” ( r ∼ 20 − 5 + 8 pc) appears redder ( β ∼ −2 ± 0.2), likely because it is older (100–200 Myr) with mild dust extinction ( A V ∼ 0.1 mag). With an estimated stellar mass ratio of roughly 2:1 and physical projected separation ∼400 pc, we may be witnessing a galaxy merger 430 million years after the Big Bang. We identify galaxies with similar colors in a high-redshift simulation, finding their star formation histories to be dissimilar, which is also suggested by the spectral energy distribution fitting, suggesting they formed further apart. We also identify a candidate companion galaxy “C” ∼3 kpc away, likely destined to merge with A and B. Upcoming JWST Near Infrared Spectrograph observations planned for 2023 January will deliver spectroscopic redshifts and more physical properties for these tiny magnified distant galaxies observed in the early universe.
Publisher: American Astronomical Society
Date: 26-10-2023
Publisher: Oxford University Press (OUP)
Date: 28-07-2023
Abstract: We use the astraeus framework to investigate how the visibility and spatial distribution of Lyman-α (Lyα) emitters (LAEs) during reionization is sensitive to a halo mass-dependent fraction of ionizing radiation escaping from the galactic environment (fesc) and the ionization topology. To this end, we consider the two physically plausible bracketing scenarios of fesc increasing and decreasing with rising halo mass. We derive the corresponding observed Lyα luminosities of galaxies for three different analytic Lyα line profiles and associated Lyα escape fraction ($f_\\mathrm{esc}^\\mathrm{Ly\\alpha }$) models: importantly, we introduce two novel analytic Lyα line profile models that describe the surrounding interstellar medium (ISM) as dusty gas clumps. They are based on parameterizing results from radiative transfer simulations, with one of them relating $f_\\mathrm{esc}^\\mathrm{Ly\\alpha }$ to fesc by assuming the ISM of being interspersed with low-density tunnels. Our key findings are: (i) for dusty gas clumps, the Lyα line profile develops from a central to double peak dominated profile as a galaxy’s halo mass increases (ii) LAEs are galaxies with $M_h\\gtrsim 10^{10}\\, {\\rm \\rm M_\\odot }$ located in overdense and highly ionized regions (iii) for this reason, the spatial distribution of LAEs is primarily sensitive to the global ionization fraction and only weakly in second-order to the ionization topology or a halo mass-dependent fesc (iv) furthermore, as the observed Lyα luminosity functions reflect the Lyα emission from more massive galaxies, there is a degeneracy between the fesc-dependent intrinsic Lyα luminosity and the Lyα attenuation by dust in the ISM if fesc does not exceed $\\sim 50~{{\\ \\rm per \\, cent}}$.
Publisher: Oxford University Press (OUP)
Date: 03-08-2023
Abstract: We explore how the characteristics of the cross-correlation functions between the 21-cm emission from the spin-flip transition of neutral hydrogen (H $\\scriptstyle \\rm I $) and early Lyman α (Ly α) radiation emitting galaxies (Ly α emitters, LAEs) depend on the reionization history and topology and the simulated volume. For this purpose, we develop an analytic expression for the 21-cm-LAE cross-correlation function and compare it to results derived from different astraeus and 21cmfast reionization simulations covering a physically plausible range of scenarios where either low-mass (≲ 109.5 M⊙) or massive (≳ 109.5 M⊙) galaxies drive reionization. Our key findings are: (i) the negative small-scale (≲ 2 cMpc) cross-correlation litude scales with the intergalactic medium’s (IGM) average H $\\scriptstyle \\rm I $ fraction (〈χH i〉) and spin-temperature weighted overdensity in neutral regions (〈1 + δ〉H i) (ii) the inversion point of the cross-correlation function traces the peak of the size distribution of ionized regions around LAEs (iii) the cross-correlation litude at small scales is sensitive to the reionization topology, with its anticorrelation or correlation decreasing the stronger the ionizing emissivity of the underlying galaxy population is correlated to the cosmic web gas distribution (i.e. the more low-mass galaxies drive reionization) (iv) the required simulation volume to not underpredict the 21-cm-LAE anticorrelation litude when the cross-correlation is derived via the cross-power spectrum rises as the size of ionized regions and their variance increases. Our analytic expression can serve two purposes: to test whether simulation volumes are sufficiently large, and to act as a fitting function when cross-correlating future 21-cm signal Square Kilometre Array and LAE galaxy observations.
Publisher: American Astronomical Society
Date: 04-2022
Abstract: We present two bright galaxy candidates at z ∼ 12–13 identified in our H -dropout Lyman break selection with 2.3 deg 2 near-infrared deep imaging data. These galaxy candidates, selected after careful screening of foreground interlopers, have spectral energy distributions showing a sharp discontinuity around 1.7 μ m, a flat continuum at 2–5 μ m, and nondetections at .2 μ m in the available photometric data sets, all of which are consistent with a z 12 galaxy. An ALMA program targeting one of the candidates shows a tentative 4 σ [O iii ] 88 μ m line at z = 13.27, in agreement with its photometric redshift estimate. The number density of the z ∼ 12–13 candidates is comparable to that of bright z ∼ 10 galaxies and is consistent with a recently proposed double-power-law luminosity function rather than the Schechter function, indicating little evolution in the abundance of bright galaxies from z ∼ 4 to 13. Comparisons with theoretical models show that the models cannot reproduce the bright end of rest-frame ultraviolet luminosity functions at z ∼ 10–13. Combined with recent studies reporting similarly bright galaxies at z ∼ 9–11 and mature stellar populations at z ∼ 6–9, our results indicate the existence of a number of star-forming galaxies at z 10, which will be detected with upcoming space missions such as the James Webb Space Telescope, Nancy Grace Roman Space Telescope, and GREX-PLUS.
Publisher: American Astronomical Society
Date: 06-2022
Abstract: The Reionization Era Bright Emission Line Survey (REBELS) is a cycle-7 ALMA Large Program (LP) that is identifying and performing a first characterization of many of the most luminous star-forming galaxies known in the z 6.5 universe. REBELS is providing this probe by systematically scanning 40 of the brightest UV-selected galaxies identified over a 7 deg 2 area for bright [C ii ] 158 μ m and [O iii ] 88 μ m lines and dust-continuum emission. Selection of the 40 REBELS targets was done by combining our own and other photometric selections, each of which is subject to extensive vetting using three completely independent sets of photometry and template-fitting codes. Building on the observational strategy deployed in two pilot programs, we are increasing the number of massive interstellar medium (ISM) reservoirs known at z 6.5 by ∼4–5× to . In this manuscript, we motivate the observational strategy deployed in the REBELS program and present initial results. Based on the first-year observations, 18 highly significant ≥ 7 σ [C ii ] 158 μ m lines have already been discovered, the bulk of which (13/18) also show ≥3.3 σ dust-continuum emission. These newly discovered lines more than triple the number of bright ISM-cooling lines known in the z 6.5 universe, such that the number of ALMA-derived redshifts at z 6.5 rival Ly α discoveries. An analysis of the completeness of our search results versus star formation rate (SFR) suggests an ∼79% efficiency in scanning for [C ii ] 158 μ m when the SFR UV+IR is M ⊙ yr −1 . These new LP results further demonstrate ALMA’s efficiency as a “redshift machine,” particularly in the Epoch of Reionization.
Publisher: Oxford University Press (OUP)
Date: 09-05-2023
Abstract: We present Atacama Large Millimeter/Submillimeter Array (ALMA) [C ii] and ∼158 $\\rm \\mu m$ continuum observations of REBELS-25, a massive, morphologically complex ultra-luminous infrared galaxy (ULIRG LIR = $1.5^{+0.8}_{-0.5} \\times 10^{12}$ L⊙) at z = 7.31, spectroscopically confirmed by the Reionization Era Bright Emission Line Survey (REBELS) ALMA Large Programme. REBELS-25 has a significant stellar mass of $M_{*} = \\mbox{$ 8^{+4}_{-2} \\times 10^{9} $}{} ~\\mbox{M$_\\odot $}{}$. From dust-continuum and ultraviolet observations, we determine a total obscured + unobscured star formation rate of SFR $= \\mbox{$199^{+101}_{-63}$}{} ~ \\mbox{M$_\\odot $}~ \\mbox{${\\rm yr}$}^{-1}$. This is about four times the SFR estimated from an extrapolated main sequence. We also infer a [C ii]-based molecular gas mass of $M_{{\\rm H}_{2}} = \\mbox{$5.1^{+5.1}_{-2.6} \\times 10^{10}$}{} ~\\mbox{M$_\\odot $}{}$, implying a molecular gas depletion time of $t_{\\rm depl, {\\rm H}_{2}} = \\mbox{$0.3^{+0.3}_{-0.2} $}{}$ Gyr. We observe a [C ii] velocity gradient consistent with disc rotation, but given the current resolution we cannot rule out a more complex velocity structure such as a merger. The spectrum exhibits excess [C ii] emission at large positive velocities (∼500 km s−1), which we interpret as either a merging companion or an outflow. In the outflow scenario, we derive a lower limit of the mass outflow rate of 200 $\\mbox{M$_\\odot $}~ \\mbox{${\\rm yr}$}^{-1}$, which is consistent with expectations for a star-formation-driven outflow. Given its large stellar mass, SFR, and molecular gas reservoir ∼700 Myr after the big bang, we explore the future evolution of REBELS-25. Considering a simple, conservative model assuming an exponentially declining star formation history, constant star formation efficiency, and no additional gas inflow, we find that REBELS-25 has the potential to evolve into a galaxy consistent with the properties of high-mass quiescent galaxies recently observed at z ∼ 4.
Publisher: American Astronomical Society
Date: 08-2022
Abstract: We present the average [C ii ] 158 μ m emission line sizes of UV-bright star-forming galaxies at z ∼ 7. Our results are derived from a stacking analysis of [C ii ] 158 μ m emission lines and dust continua observed by the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of the large program Reionization Era Bright Emission Line Survey. We find that the average [C ii ] emission at z ∼ 7 has an effective radius r e of 2.2 ± 0.2 kpc. It is ≳2× larger than the dust continuum and the rest-frame UV emission, in agreement with recently reported measurements for z ≲ 6 galaxies. Additionally, we compared the average [C ii ] size with 4 z 6 galaxies observed by the ALMA Large Program to INvestigate [C ii ] at Early times (ALPINE). By analyzing [C ii ] sizes of 4 z 6 galaxies in two redshift bins, we find an average [C ii ] size of r e = 2.2 ± 0.2 kpc and r e = 2.5 ± 0.2 kpc for z ∼ 5.5 and z ∼ 4.5 galaxies, respectively. These measurements show that star-forming galaxies, on average, show no evolution in the size of the [C ii ] 158 μ m emitting regions at redshift between z ∼ 7 and z ∼ 4. This finding suggests that the star-forming galaxies could be morphologically dominated by gas over a wide redshift range.
Publisher: Oxford University Press (OUP)
Date: 29-07-2023
Abstract: We present the results of a search for high-redshift (z & 9) galaxy candidates in the JWST UNCOVER survey, using deep NIRCam and NIRISS imaging in seven bands over ∼45 arcmin2 and ancillary Hubble Space Telescope (HST) observations. The NIRCam observations reach a 5σ limiting magnitude of ∼29.2 AB. The identification of high-z candidates relies on a combination of a dropout selection and photometric redshifts. We find 16 candidates at 9 & z & 12 and three candidates at 12 & z & 13, eight candidates are deemed very robust. Their lensing lification ranges from μ = 1.2 to 11.5. Candidates have a wide range of (lensing corrected) luminosities and young ages, with low stellar masses [6.8 & log(M⋆/M⊙) & 9.5] and low star formation rates (SFR = 0.2–7 M⊙ yr−1), confirming previous findings in early JWST observations of z & 9. A few galaxies at z ∼ 9−10 appear to show a clear Balmer break between the F356W and F444W/F410M bands, which helps constrain their stellar mass. We estimate blue UV continuum slopes between β = −1.8 and −2.3, typical for early galaxies at z & 9 but not as extreme as the bluest recently discovered sources. We also find evidence for a rapid redshift-evolution of the mass-luminosity relation and a redshift evolution of the UV continuum slope for a given range of intrinsic magnitude, in line with theoretical predictions. These findings suggest that deeper JWST observations are needed to reach the fainter galaxy population at those early epochs, and follow-up spectroscopy will help better constrain the physical properties and star formation histories of a larger s le of galaxies.
Publisher: American Astronomical Society
Date: 25-07-2023
Abstract: Recent JWST/NIRCam imaging taken for the ultra-deep UNCOVER program reveals a very red dropout object at z phot ≃ 7.6, triply imaged by the galaxy cluster A2744 ( z d = 0.308). All three images are very compact, i.e., unresolved, with a delensed size upper limit of r e ≲ 35 pc. The images have apparent magnitudes of m F444W ∼ 25−26 AB, and the magnification-corrected absolute UV magnitude of the source is M UV,1450 = −16.81 ± 0.09. From the sum of observed fluxes and from a spectral energy distribution (SED) analysis, we obtain estimates of the bolometric luminosities of the source of L bol ≳ 10 43 erg s −1 and L bol ∼ 10 44 –10 46 erg s −1 , respectively. Based on its compact, point-like appearance, its position in color–color space, and the SED analysis, we tentatively conclude that this object is a UV-faint dust-obscured quasar-like object, i.e., an active galactic nucleus at high redshift. We also discuss other alternative origins for the object’s emission features, including a massive star cluster, Population III, supermassive, or dark stars, or a direct-collapse black hole. Although populations of red galaxies at similar photometric redshifts have been detected with JWST, this object is unique in that its high-redshift nature is corroborated geometrically by lensing, that it is unresolved despite being magnified—and thus intrinsically even more compact—and that it occupies notably distinct regions in both size–luminosity and color–color space. Planned UNCOVER JWST/NIRSpec observations, scheduled in Cycle 1, will enable a more detailed analysis of this object.
Start Date: 2014
End Date: 12-2017
Amount: $360,000.00
Funder: Australian Research Council
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