Is the IMF in ellipticals bottom-heavy? Clues from their chemical abundances

© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.We tested the implementation of different initial mass functions (IMFs) in our model for the chemical evolution of ellipticals, with the aim of reproducing the observed relations of [Fe/H] and [Mg/Fe] abundances with galaxy mass in a sample of early-type galaxies selected from the SPIDER-SDSS catalogue. Abundances in the catalogue were derived from averaged spectra, obtained by stacking individual spectra according to central velocity dispersion, as a proxy of galaxy mass. We tested IMFs already used in a previous work, as well as two new models, based on low-mass tapered (‘bimodal’) IMFs, where the IMF becomes either (1) bottom-heavy in more massive galaxies, or (2) is time-dependent, switching from top-heavy to bottom-heavy in the course of galactic evolution. We found that observations could only be reproduced by models assuming either a constant, Salpeter IMF, or a time-dependent distribution, as other IMFs failed. We further tested the models by calculating their M/L ratios. We conclude that a constant, time-independent bottom-heavy IMF does not reproduce the data, especially the increase of the [α/Fe] ratio with galactic stellar mass, whereas a variable IMF, switching from top to bottom-heavy, can match observations. For the latter models, the IMF switch always occurs at the earliest possible considered time, i.e. tswitch = 0.1 Gyr.Peer reviewe

Deciphering the local Interstellar spectra of primary cosmic ray species with HelMod

Local interstellar spectra (LIS) of primary cosmic ray (CR) nuclei, such as helium, oxygen, and mostly primary carbon are derived for the rigidity range from 10 MV to ~200 TV using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. Two propagation packages, GALPROP and HelMod, are combined into a single framework that is used to reproduce direct measurements of CR species at different modulation levels, and at both polarities of the solar magnetic field. The developed iterative maximum-likelihood method uses GALPROP-predicted LIS as input to HelMod, which provides the modulated spectra for specific time periods of the selected experiments for model-data comparison. The interstellar and heliospheric propagation parameters derived in this study are consistent with our prior analyses using the same methodology for propagation of CR protons, helium, antiprotons, and electrons. The resulting LIS accommodate a variety of measurements made in the local interstellar space (Voyager 1) and deep inside the heliosphere at low (ACE/CRIS, HEAO-3) and high energies (PAMELA, AMS-02).Comment: 13 pages, 13 figures, 6 tables, ApJ in press. arXiv admin note: text overlap with arXiv:1704.0633

HelMod in the works: from direct observations to the local interstellar spectrum of cosmic-ray electrons

The local interstellar spectrum (LIS) of cosmic-ray (CR) electrons for the energy range 1 MeV to 1 TeV is derived using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. Two propagation packages, GALPROP and HelMod, are combined to provide a single framework that is run to reproduce direct measurements of CR species at different modulation levels, and at both polarities of the solar magnetic field. An iterative maximum-likelihood method is developed that uses GALPROP-predicted LIS as input to HelMod, which provides the modulated spectra for specific time periods of the selected experiments for model-data comparison. The optimized HelMod parameters are then used to adjust GALPROP parameters to predict a refined LIS with the procedure repeated subject to a convergence criterion. The parameter optimization uses an extensive data set of proton spectra from 1997-2015. The proposed CR electron LIS accommodates both the low-energy interstellar spectra measured by Voyager 1 as well as the high-energy observations by PAMELA and AMS-02 that are made deep in the heliosphere; it also accounts for Ulysses counting rate features measured out of the ecliptic plane. The interstellar and heliospheric propagation parameters derived in this study agree well with our earlier results for CR protons, helium nuclei, and anti-protons propagation and LIS obtained in the same framework.Comment: 11 pages, 14 figures, 4 tables; ApJ, in pres

BfpI, BfpJ, and BfpK Minor Pilins Are Important for the Function and Biogenesis of Bundle-Forming Pili Expressed by Enteropathogenic Escherichia coli

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Pemanfaatan Media Sosial Sebagai Sarana Komunikasi dalam Pencegahan Meluasnya Wabah COVID-19 di Kalangan Pelajar

Kegiatan pengabdian kepada masyarakat ini melibatkan 10 orang mahasiswa untuk memberikan edukasi kepada para pelajar dalam bentuk pemanfaatan media sosial sebagai sarana komunikasi dalam pencegahan meluasnya wabah Covid-19. Peserta KKN-Tematik akan merancang konten dalam bentuk infografis dan video untuk memberikan edukasi kepada pelajar melalui media sosial para pelajar. Waktu pelaksanaan kegiatan ini mulai tanggal 11 Juni 2020 sampai 11 Juli 2020. Lokasi pelaksanaan kegiatan pengabdian ini dilaksanakan sesuai dengan domisili wilayah peserta KKN-Tematik dengan objek sasaran kegiatan yaitu para pelajar jenjang SMP, SMA, SMK. Hasil kegiatan pengabdian ini menunjukkan bahwa program pengabdian terlaksana dengan baik sehingga pemanfaatan media sosial para pelajar memberikan pengaruh yang positif terhadap pencegahan meluasnya wabah Covid-19 di kalangan pelajar. Hal ini ditunjukkan dengan terdapat 40 poster dan 10 video edukasi yang dihasilkan oleh peserta KKN-Tematik, masing-masing peserta telah menjangkau akun media sosial para pelajar melewati 10 orang, dan siswa memiliki respon positif terhadap pelaksaaan kegiatan KKN-Tematik ini

Study of Structure Activity Correlation of 7-O-Amide Hesperetine Derivative based on Descriptor Calculation by Using AM1 as Anti-Inflammatory Candidate

This study aims to study the quantitative relationship between molecular structure and biological activity (QSAR) of the 7-O-amide hesperetine derivative compounds and to design new compounds which are more potential as anti-inflammatory. This research was theoretically exploratory by using computational chemical methods. The object of this research was 23 derivative compounds of 7-O-Amide Hesperetine with their anti-inflammatory biological activity (IC50) values. The research data were obtained from the results of quantum chemistry calculations assist with computational chemistry code and statistical analysis of multiple linear regressions. The QSAR equation obtained was log IC50 = -2581,151 + (3127,454 × qC2) + (1884,436 × qC3) + (-1581,855 × qC11) + (8181,049 × qC8) + (-2166,325 ×qC4), where n = 23, R2 = 0.679, SEE = 0.092, Fcount /Ftable = 7189, and PRESS = 0.144. The best QSAR model was used to design and predict 23 new anti-inflammatory compounds of derived from 7-O-amide hesperetine with higher activity. The calculation results showed that the proposed anti-inflammatory compound with the highest activity to prevent inflammation was (S)-5-hydroxy-2-(3hidroxy-4-methoxyphenyl)-7-(2-oxo-2-(piperazine-1-yl)ethoxy )chroman-4-one (compound 38) with an IC50 value of 1.194 or 15.66 nM

Dark energy interacting with two fluids

A cosmological model of dark energy interacting with dark matter and another general component of the universe is investigated. We found general constraints on these models imposing an accelerated expansion. The same is also studied in the case for holographic dark energy