Elemental compositions of hyper-metal-poor stars formed in dust-enricheddense shells of population III supernova remnants
Takaya Nozawa, Takashi Kozasa, Ken'ichi Nomoto, Keiichi Maeda, Nozomu Tominaga et al.
Citation: AIP Conf. Proc. 1480, 400 (2012); doi: 10.1063/1.4754400
View online: http://dx.doi.org/10.1063/1.4754400
View Table of Contents: http://proceedings.aip.org/dbt/dbt.jsp?KEY=APCPCS&Volume=1480&Issue=1
Published by the American Institute of Physics.

Related Articles
Iteration stability for simple Newtonian stellar systems
J. Math. Phys. 50, 073505 (2009)
Accretion disk dynamics, photoionized plasmas, and stellar opacities
Phys. Plasmas 16, 041001 (2009)
Radiating relativistic matter in geodesic motion
J. Math. Phys. 50, 022502 (2009)
Tikekar superdense stars in electric fields
J. Math. Phys. 48, 042501 (2007)
Bounds on the dragging rate of slowly and differentially rotating relativistic stars
J. Math. Phys. 45, 3379 (2004)

Additional information on AIP Conf. Proc.
Journal Homepage: http://proceedings.aip.org/
Journal Information: http://proceedings.aip.org/about/about_the_proceedingsTop downloads: http://proceedings.aip.org/dbt/most_downloaded.jsp?KEY=APCPCS
Information for Authors: http://proceedings.aip.org/authors/information_for_authors

Downloaded 23 Sep 2012 to 157.82.226.85. Redistribution subject to AIP license or copyright; see http://proceedings.aip.org/about/rights_permissions

Elemental Compositions of Hyper-Metal-PoorStars Formed in Dust-Enriched Dense Shells ofPopulation III Supernova Remnants
Takaya Nozawa∗ , Takashi Kozasa† , Ken’ichi Nomoto∗ , Keiichi Maeda∗ ,Nozomu Tominaga∗∗ , Hideyuki Umeda‡ and Asao Habe†∗Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for
Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8583, Japan†
Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo060-0810, Japan∗∗
Department of Physics, Faculty of Science and Engineering, Konan University, Okamoto, Kobe658-8501, Japan‡
Department of Astronomy, School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033,
JapanAbstract. We describe the evolution of dust within Population III supernova remnants (SNRs) andinvestigate the chemical compositions of the dust piled up in their dense shells. We show that theresulting abundance patterns of the major elements in the dense shells are in good agreement withthat observed for a Galactic halo star, SDSS J102915+172927. This allows us to propose that SDSSJ102915+172927 might be the second-generation star formed in the dust-enriched dense shell of aPopulation III SNR. We conclude that the segregation of dust from the metal-rich ejecta gas can be
an important process in determining the abundance patterns of primitive low-mass stars.
Keywords: dust, extinction – ISM: supernova remnants – supernovae: general – stars: abundances,stars; chemically peculiar – stars: low-mass
PACS: 97.10.Bt, 97.10.Tk, 97.20.Tr, 97.60.Bw, 98.38.Cp, 98.38.Mz

INTRODUCTION
Hyper-metal-poor stars with [Fe/H] ≤ −5 are considered to be vestiges of stellar populations in the early universe [1]. Since they must have been formed in very little enriched
gas clouds, their chemical compositions are expected to reflect the nucleosynthesis in
the very early generations of stars [2–6]. Such old metal-poor stars also provide deep
insight into the formation mechanism of low-mass (≤ 1 M ) stars in low-metallicity environments. The most primitive Galactic star discovered so far, SDSS J102915+172927
shows an extremely low metal content (Z ≤ 4.5 × 10−5 Z ) [7], suggesting that the formation of this star must have been induced through the cooling by dust grains [8, 9].
Here we propose one possible scenario for the origin of SDSS J102915+172927; thisstar might be the second-generation star that was formed in the dust-enriched dense shellof a Population III supernova remnant (SNR). This scenario can naturally explain (1) thepresence of dust grains necessary for the formation of sub-solar mass stars and (2) theabundance pattern of the major elements observed for SDSS J102915+172927. In thefollowings, we briefly describe the evolution of newly formed dust in SNRs and analyze
the elemental compositions of the dust grains accumulated in the dense SN shells.

FIRST STARS IV -From Hayashi to the FutureAIP Conf. Proc. 1480, 400-402 (2012); doi: 10.1063/1.4754400© 2012 American Institute of Physics 978-0-7354-1092-3/$30.00

400
Downloaded 23 Sep 2012 to 157.82.226.85. Redistribution subject to AIP license or copyright; see http://proceedings.aip.org/about/rights_permissions

EVOLUTION OF DUST IN POP III SNRSThe evolution of dust inside SNRs is described in detail in [10], where we calculated
the dynamics of dust and its destruction by sputtering, based on the size distribution andspatial distribution of dust formed in the unmixed ejecta of Population III core-collapse
supernovae (SNe) [11]. The time evolution of the gas temperature and density in SNRs
are also computed for the uniform interstellar medium (ISM) with the hydrogen number
density of nH,0 = 0.1, 1.0, and 10 cm−3 . As the initial condition of the gas in the ejecta,
we adopted the hydrodynamic models of Population III SNe with the progenitor massesof MZAMS = 13, 20, 25, and 30 M , all of which have explosion energy of 1051 erg [12].
The results of the calculations show that the evolution of dust in SNRs heavily dependon their initial radii aini . For nH,0 = 1.0 cm−3 , small grains with aini < 0.05 µ m aretrapped in the shocked hot gas and are completely destroyed through thermal sputtering.
Grains with aini  0.05–0.2 µ m reduce their radii by ∼50% but are eventually piled
up in the dense shell behind the forward shocks. Large grains of aini > 0.2 µ m are
injected into the ISM without being decelerated and eroded significantly, Note that thetransport and destruction of dust in SNRs also depend on the density of gas in the ISM;
for a higher ISM density, dust grains undergo more efficient deceleration and erosion,and thus the majority of newly formed grains are destroyed for nH,0 = 10 cm−3 .

ELEMENTAL COMPOSITIONS IN DENSE SN SHELLSThe calculations of dust evolution within SNRs indicate that a part of the dust grains
surviving the destruction are finally incorporated into the dense SN shells. These piledup grains can drive the formation of sub-solar mass stars in the shells [13] and affectsignificantly the elemental abundances of the newly formed stars. Therefore, assumingthat the composition of the piled-up grains determines the elemental composition of
those low-mass stars, we derive the metal abundances in the dense shells of Population
III SNRs and compare to those observed for SDSS J102915+172927.
Figure 1 shows the calculated abundances of C, O, Mg, and Si relative to Fe in theshells. For nH,0 = 0.1 and 1.0 cm−3 , the metallicity in the shells is less than 4.5 × 10−5Z , and the iron abundances are in the range of [Fe/H]  −6 to −5, both of which arein good agreement with those for SDSS J102915+172927 (see [10, 14] for the tabulated
values of the elemental abundances and metallicity in the dense SN shells). It can beseen that most of the models show the modest overabundances of C and Si (0.1 ≤ [C/Fe]≤ 1.1 and 0.4 ≤ [Si/Fe] ≤ 1.3) and the nearly solar abundances of O and Mg (−0.7 ≤[O/Fe] ≤ 0.6 and −0.5 ≤ [Mg/Fe] ≤ 0.7), except for one or two extreme cases. Thesetendencies are entirely consistent with the abundance pattern of SDSS J102915+172927.
In particular, the results for MZAMS = 30 M and nH,0 = 0.1 cm−3 (open triangles) andMZAMS = 25 M and nH,0 = 1.0 cm−3 (open circles) well match the observed abundancesof the major elements. Thus, these results suggest that SDSS J102915+172927 could
be the second-generation star that was formed in the dust-enriched dense shell of aPopulation III SNR. We conclude that the formation of dust in the SN ejecta and thesubsequent decoupling of the dust from metal-rich ejecta can be critical processes toform the primitive low-mass stars such as SDSS J102915+172927.

401
Downloaded 23 Sep 2012 to 157.82.226.85. Redistribution subject to AIP license or copyright; see http://proceedings.aip.org/about/rights_permissions

FIGURE 1. Abundances of C, O, Mg, and Si relative to Fe derived from the chemical compositions ofdust grains piled up in the dense shells of Population III SNRs that expand into the uniform ISM withnH,0 = 0.1 cm−3 (triangles) and nH,0 = 1.0 cm−3 (circles). Models of core-collapse SNe with MZAMS =13, 20, 25, and 30 M are taken from [12]. The observed elemental abundances (and upper limits) of a
Galactic halo star SDSS J102915+172927 are plotted by the red crosses (with the arrows) [7]. The open
triangles and circles are, respectively, the results for the models with MZAMS = 30 M and nH,0 = 0.1
cm−3 , and MZAMS = 25 M and nH,0 = 1.0 cm−3 . which show the best agreement with the observed
elemental composition of SDSS J102915+172927 among the models considered here.

ACKNOWLEDGMENTS
This research has been supported in part by World Premier International ResearchCenter Initiative (WPI Initiative), MEXT, Japan, and by the Grant-in-Aid for Scientific
Research of the Japan Society for the Promotion of Science (22684004, 23224004).

REFERENCES
1. Beers, T., & Christlieb, N., ARAA, 43, 531–580 (2005)
2. Limongi, M., Chieffi, A., & Bonifacio, P., ApJ, 594, L123–L126 (2003)
3. Suda, T., Aikawa, M., Machida, M. N., Fujimoto, M. Y., & Iben, I. Jr., ApJ, 611, 476–493 (2004)
4. Iwamoto, N., Umeda, H., Tominaga, N., Nomoto, K., & Maeda, K., Science, 309, 451–453 (2005)
5. Tominaga, N., Umeda, H., & Nomoto, K., ApJ, 660, 516–540 (2007)
6. Heger, A., & Woosley, S. E., ApJ, 724, 341–373 (2010)
7. Caffau, E., et al., Nature, 477, 67–69 (2011)
8. Klessen, R. S., Glover, S. C. O., & Clark, P. C., MNRAS, 421, 3217–3221 (2012)
9. Schneider, R., Omukai, K., Limongi, M., Ferrara, A., Salvaterra, R., Chieffi, A., & Bianchi, S.,
MNRAS, 423, L60–L64 (2012)
10. Nozawa, T., et al., ApJ, 666, 955–966 (2007)
11. Nozawa, T., Kozasa, T., Umeda, H., Maeda, K., & Nomoto, K., ApJ, 598, 785–803 (2003)
12. Umeda, H., & Nomoto, K., ApJ, 565, 385–404 (2002)
13. Chiaki, G., Yoshida, N., & Kitayama, T., ApJ, submitted (2012) (arXiv:1203.0820)
14. Nozawa, T., et al., Cosmic Dust - Near and Far - 2008, edited by Th. Henning, E. Grün, and J.
Steinacker, ASP Conference Series 414, Astronomical Society of the Pacific, San Francisco, 2009, pp.
247–265.

402
Downloaded 23 Sep 2012 to 157.82.226.85. Redistribution subject to AIP license or copyright; see http://proceedings.aip.org/about/rights_permissions