IDEAS (IPMU Day of Extragalactic Astrophysics Seminars) on Chemical Evolution

Aim

IDEAS (IPMU Day of Extragalactic Astrophysics Seminars) is a new initiative at IPMU to hold a series of one-day workshops (~3 per year) on a particular topic in astrophysics. The aim is to foster further interaction between astrophysicists in the Tokyo metropolitan area (including those from greater distances), and allow students and postdocs to share results in front of an international audience.

We have scheduled the first of such a series to be held on Tuesday, July 13th. The kickoff meeting will cover the topic of chemical evolution. There will be lectures spread over the day as listed here.

Date

July 13th (Tuesday), 10:30 -

Place

IPMU, seminar room B

Program

10:30 - 11:30 Keiichi Maeda
Supernova Nucleosynthesis
11:30 - 12:30 Kyoko Matsushita
Observations of metals in hot interstellar and intracluster medium
12:30 - 14:00 Lunch Break
14:00 - 15:00 Wako Aoki
Extremely metal-poor stars in the Milky Way and dwarf galaxies
15:00 - 16:00 Coffee Break
16:00 - 16:20 Ko Nakamura
Light Element Synthesis in Core-collapse Supernovae
16:20 - 16:40 Takashi Yoshida
Nucleosynthesis and Mixing in Supernovae Reproducing Isotopic Ratios of Presolar Grains
16:40 - 17:00 Natsuko Izutani
Nucleosynthesis in High-Entropy Hot-Bubbles of SNe and Abundance Patterns of Extremely Metal-Poor Stars
17:00 - 17:20 Mark Vagins
GADZOOKS!  Supernova Neutrinos Without The Annoying Wait
17:20 - 17:40 Kentaro Nagamine
Constraining feedback models with cosmological chemical evolution
18:00 - Going out for dinner
Place: a Spanish restaurant near JR Kashiwa station
Fee: ~ 4,000 JPY/person (being payed on sight)

Abstract

Keiichi Maeda

Supernovae play major roles in producing heavy elements in the Universe. In this talk, I first summarize basics aspects of explosive nucleosynthesis in supernovae. Then I discuss how different populations of supernovae, including recently discovered possible new classes, could produce different necleosynthesis yields.


Kyoko Matsushita

We derived radial abundance profiles of O, Mg, Si, S and Fe in the intracluster medium (ICM) of several clusters and groups of galaxies up to $\sim$0.3{180}$ with Suzaku and those of Fe in 28 nearby brightest clusters of galaxies up to 0.3-0.5 {180}$ with XMM.

Within 0.05{180}$, Fe abundance scatters from 0.5 to 1 solar. The scatter may be caused by a difference in recent metal supplies with supernovae Ia and stellar mass loss from cD galaxies.

In these regions the abundance patterns of O, Mg, Si, S and Fe are close to the solar ratio adopting the new solar abundance defined by Loddars (2003). At 0.1--0.5{180}$, relaxed clusters with a cD galaxy at their X-ray peak have flat Fe abundance profiles at 0.4--0.5 solar, with a small scatter.

In these clusters, the ratio of Fe mass in the ICM to the light from galaxies have similar profiles, and increases toward outer regions. In addition, several systems show a hint of enhancement of O/Fe and Mg/Fe ratios. These results indicate that the metal-enrichment process in these clusters would have been universal, and a significant amount of Fe is synthesized at a very early stage in cluster formation.

Suzaku also derived O, Mg, Si and Fe abundances in hot interstellar medium (ISM) in several galaxies.

The derived Fe abundances of the ISM in elliptical galaxies are about 0.5--1.0 solar, indicating a low rate of present metal supply into the ICM.

To account for Fe mass in the ICM, the past average rate of SNe Ia was much larger.

The derived O and Mg abundances are consistent with stellar metallicity which reflects formation histories of these galaxies.

The abundane patterns of the hot ISM in spiral galaxies depend on their starburst activities.


Wako Aoki

I report our recent efforts to understand the early generations of stars in the Milky Way. The topics are chemical abundances of Milky Way halo stars recently discovered by SDSS and of extremely metal-poor stars in dwarf galaxies around the Milky Way. Recent discussions on the connection between the Milky Way halo and dwarf galaxies are reviewed.


Ko Nakamura

As massive stars collapse, neutrinos are emitted in large numbers from the central remnants. Some of the neutrinos interact with nuclei in the exploding materials and induce light element synthesis such as 7Li and 11B. Subsequently, the ejected material with very high energy impinge on the interstellar/circumstellar matter and spallate into light elements including Be. The latter process is possible for Type Ic supernova (SN Ic), the progenitors of which have lost their N/He envelopes via strong mass loss and possess very compact structure like Wolf-Rayet stars. The contributions of SNe Ic to the Galactic chemical evolution and the observed abundances of the light elements on halo stars will be discussed.


Takashi Yoshida

Presolar grains in primitive meteorites are considered to have traces of the nucleosynthesis at their birth as large isotopic anomalies. A small population of SiC and low density graphite indicate excesses of 28Si so that they are considered to originate from supernovae. Some of the grains also show the presence of radiogenic 44Ca from the decay of 44Ti. These isotopic signatures can be explained by the nucleosynthesis in deep region of supernova ejecta. However, carbon-enriched environment where SiC and graphite form is found only in outer He-rich layer. Therefore, in order to reproduce isotopic and elemental signatures of presolar grains from supernovae, large-scale heterogeneous mixing in supernova ejecta is required.

We calculate supernova nucleosynthesis to obtain isotopic distribution of supernova ejecta. Then, we divide the supernova ejecta into seven distinct layers and investigate the mixtures reproducing C, N, O, Al, Si, and Ti isotopic ratios of individual grains under the elemental composition condition N(C) > N(O).

The mixing ratios of the mixtures depend on the isotopic ratios of the grains.

The main component of the mixtures is one of outer He/C and He/N layers and innermost Ni layer. We will show some elemental features of the mixtures.

We will also discuss prospects for grain formation and explosion mechanism of supernovae.


Natsuko Izutani

There have been suggestions that the abundance of Extremely Metal-Poor (EMP) stars can be reproduced by Hypernovae (HNe), not by normal supernovae (SNe).

However, recently it was also suggested that if the innermost neutron-rich or proton-rich matter is ejected, the abundance patterns of ejected matter is changed, and normal SNe may also reproduce the observations of EMP stars.

We calculate explosive nucleosynthesis with various Ye and entropy, and investigate whether normal SNe with this innermost matter, which we call ``hot-bubble' component, can reproduce the abundance of EMP stars.

We find that neutron-rich (Ye = 0.45-0.49) and proton-rich (Ye = 0.51-0.55) matter can increase Zn/Fe and Co/Fe ratios as observed, but tend to overproduce other Fe-peak elements.

In addition to it, we find that if slightly proton-rich matter with 0.50 <= Ye < 0.501 of s/kb ~ 15-40 is ejected as much as ~ 0.06 Msolar, even normal SNe can reproduce the abundance of EMP stars, though it requires fine tuning of Ye. On the other hand, HNe can more easily reproduce the observations of EMP stars without fine-tuning. Our results imply that HNe are the most possible origin of the abundance pattern of EMP stars.


Mark Vagins

Water Cherenkov detectors have been used for many years to study neutrino interactions and search for nucleon decays.
Super-Kamiokande, at 50 kilotons the largest such underground detector in the world, has enjoyed over ten years of interesting and important physics results.  Now, a new IDEA: let's enrich Super-K with 100,000 kilograms of a water-soluble gadolinium compound!  Doing so will dramatically improve its performance as a detector for supernova neutrinos, thereby allowing the immediate discovery of the diffuse supernova neutrino background.


Kentaro Nagamine

TBA


*There will be plenty of time for discussion, informal interaction and catching up on personal email.

Contact

If you are interested in participating in this event, please send an email to John Silverman (john.silverman_at_ipmu.jp) and Keiichi Maeda (keiichi.maeda_at_ipmu.jp). Again, we fully encourage students to participate. This forum shall foster lively interaction and discussion (in English). We are also planning to go out for dinner to a local restaurant. Please indicate whether you would like to join us so that we have an accurate head count.

We look forward to your participation either in a few weeks or in a future workshop. We also welcome suggestions on topics to be addressed in future meetings.

matsushita.pdf