Day 1604

Tuesday.

1908.01559
Stellar mass -- halo mass relation for the brightest central galaxies of X-ray clusters since z~0.65
Erfanianfar, et al

We present the brightest cluster galaxies (BCGs) catalog for SPectroscoic IDentification of eROSITA Sources (SPIDERS) DR14 cluster program value-added catalog. We list the 416 BCGs identified as part of this process, along with their stellar mass, star formation rates, and morphological properties. We identified the BCGs based on the available spectroscopic data from SPIDERS and photometric data from SDSS. We computed stellar masses and SFRs of the BCGs on the basis of SDSS, WISE, and GALEX photometry using spectral energy distribution fitting. Morphological properties for all BCGs were derived by Sersic profile fitting using the software package SIGMA in different optical bands (g,r,i). We combined this catalog with the BCGs of galaxy groups and clusters extracted from the deeper AEGIS, CDFS, COSMOS, XMM-CFHTLS, and XMM-XXL surveys to study the stellar mass - halo mass relation using the largest sample of X-ray groups and clusters known to date. This result suggests that the mass growth of the central galaxy is controlled by the hierarchical mass growth of the host halo. We find a strong correlation between the stellar mass of BCGs and the mass of their host halos. This relation shows no evolution since z $\sim$ 0.65. We measure a mean scatter of 0.21 and 0.25 for the stellar mass of BCGs in a given halo mass at low ($0.1<z < 0.3$) and high ($0.3<z<0.65$) redshifts, respectively. We further demonstrate that the BCG mass is covariant with the richness of the host halos in the very X-ray luminous systems. We also find evidence that part of the scatter between X-ray luminosity and richness can be reduced by considering stellar mass as an additional variable.

1908.01598

Time lag in cosmic-ray modulation and global properties of the Solar Cycle

Bertucci, et al

When entering the heliosphere, Galactic cosmic rays (GCRs) are influenced by magnetic turbulence and Solar wind disturbances, which cause the so-called "solar modulation" effect. Understanding the time-dependent relationship between the Sun's variability and GCR flux modulation is essential for the investigation of the GCR transport processes in the heliosphere, as well as for the establishment of predictive models of GCR radiation in the interplanetary space. The known anti-correlation between GCR flux and sunspot number appears to be delayed by several months, but the origin of such a time lag is unclear. In this work, we are perform the first global characterization of the time lag evolution over the solar cycles and its energy dependence. We made use of a large collection of time-resolved data, both from space missions and ground based observatories. Since the long-term variation of the GCR flux originates by a combination of several physics processes, the investigation presented here may reveal important aspects of the GCR transport in the heliospheric plasma.

1908.01599

New results in solar modulation modeling in light of recent cosmic-ray data from space

Bertucci, et al

Thanks to space-borne experiments such as the AMS-02 and PAMELA missions in low-Earth orbit, along with the Voyager spacecrafts in the interstellar space, a large collection of multi-channel and time-resolved Galactic cosmic ray (GCR) data has recently become available. Here we present an improved measured-validated model of the "solar modulation" effect, i.e., the temporal evolution of the GCR flux inside the heliosphere caused by the 11-year variability cycle of the Sun's magnetic activity. We present our improved modeling of the structure of the heliosphere, the physical mechanisms of diffusion, drift, and energy losses of GCR particles in the heliosphere. We present our results for the temporal dependence of the key model parameters and their relationship with solar activity proxies. We discuss implications for the GCR transport in magnetic turbulence, and new insights on our understanding of the solar modulation phenomenon.

1908.01723

Constraining $\nu$-process production of Fluorine through Cosmic Ray Nucleosynthesis

Olive, Vangioni

Fluorine is massive enough that it is not considered to be a light ($Z\le5$) element, yet compared to its near neighbors, C, N, O, and Ne, it is far underproduced in the course of stellar evolution, making its origin more complex. In fact, the abundance of fluorine is the lowest among all elements between Z = 5 and 21 and is roughly 3-4 orders of magnitude below that of C, N, O, and Ne. There are several plausible sources for F beyond standard stellar evolution. These include the production in the asymptotic giant branch phase (AGB) in intermediate mass stars, production in Wolf-Rayet stars, and the production through neutrino spallation in supernovae. The latter, known as the $\nu$-process, is an important source for B11, and may contribute to the abundance of Li7 as well. We combine a simple model of Galactic chemical evolution with a standard Galactic cosmic ray nucleosynthesis model to treat self-consistently the evolution of the Li, Be, and B isotopes. We include massive star production of F, as well as contributions from AGB stars, and the $\nu$-process. Given the uncertainties in neutrino energies in supernovae, we normalize the $\nu$-process using the observed B11/B10 ratio as a constraint. As a consequence, we are able to determine the relative importance of each contribution to the F abundance. We find that although the $\nu$-process dominates at early times (low metallicity), the present-day F abundance is found to originate primarily from AGB stars.