1,720,968 research outputs found
Can Supernovae Quench Star Formation in High-z Galaxies?
Full text linkJWST is providing a unique opportunity to directly study the feedback processes regulating star formation (SF) in early galaxies. The two z > 5 quiescent systems (JADES-GS-z7-01-QU and MACS0417-z5BBG) detected so far show a recent starburst after which SF is suppressed. To clarify whether such quenching is due to supernova (SN) feedback, we have developed a minimal physical model. We derive a condition on the minimum star formation rate, , lasting for a time interval Δ t _b , required to quench SF in a galaxy at redshift z , with gas metallicity Z , and hosted by a halo of mass M _h . We find that lower ( z , Z , M _h ) systems are more easily quenched. We then apply the condition to JADES-GS-z7-01-QU ( z = 7.3, M _⋆ = 10 ^8.6 M _⊙ ) and MACS0417-z5BBG ( z = 5.2, M _⋆ = 10 ^7.6 M _⊙ ) and find that SN feedback largely fails to reproduce the observed quenched SF history. Alternatively, we suggest that SF is rapidly suppressed by radiation-driven dusty outflows sustained by the high specific star formation rates (43 and 25 Gyr ^−1 , respectively) of the two galaxies. Our model provides a simple tool to interpret the SF histories of post-starburst galaxies and unravel quenching mechanisms from incoming JWST data
Quiescent low-mass galaxies observed by JWST in the Epoch of Reionization
Full text linkThe surprising JWST discovery of a quiescent, low-mass () galaxy at redshift (JADES-GS-z7-01-QU) represents a unique
opportunity to study the imprint of feedback processes on early galaxy
evolution. We build a sample of 130 low-mass () galaxies from the SERRA cosmological zoom-in simulations, which show
a feedback-regulated, bursty star formation history (SFH). The fraction of time
spent in an active phase increases with the stellar mass from at to at , and it is in agreement with the value estimated for JADES-GS-z7-01-QU. On average, 30% of the galaxies are
quiescent in the range ; they become the dominant population at
. However, none of these quiescent
systems matches the Spectral Energy Distribution of JADES-GS-z7-01-QU, unless
their SFH is artificially truncated a few Myr after the main star formation
peak. As supernova feedback can only act on a longer timescale (), this implies that the observed abrupt quenching must be caused by a
faster physical mechanism, such as radiation-driven winds.Comment: ApJ Letters, 5 pages, 4 figure
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Temporarily Quiescent Galaxies at Cosmic Dawn: Probing Bursty Star Formation
Full text linkThe bursty, time-variable nature of star formation in the first billion years, as revealed by JWST, drives phases of temporary quiescence in low-mass galaxies that quench after starbursts. These galaxies provide unique probes of the burstiness of early star formation and its underlying physical processes. Using the serra cosmological zoom-in simulations, we analyze over 200 galaxies with M _⋆ −17. By forward modeling their spectral energy distributions, we show that they are faint (〈 M _UV 〉 = −15.6 for M _⋆ = 10 ^8 M _⊙ ), have strong Balmer breaks (>0.5), and no emission lines. Comparing our predicted fractions with JWST results, we find similar luminosity-dependent trends; however, the observed fractions of temporarily quiescent galaxies at M _UV ∼ −20 to −19 are higher, suggesting that stronger feedback or additional mechanisms beyond supernovae may be at play. We propose searching for F200W dropouts and satellites in the proximity (10 ^10 M _⊙ ) galaxies as effective strategies to uncover the hidden majority of faint ( M _UV > −17), temporarily quiescent systems, crucial for constraining early feedback processes in low-mass galaxies
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
