Has Blending Compromised Cepheid-Based Determinations of the Extragalactic Distance Scale?

We examine the suggestion that half of the HST Key Project- and Sandage/Saha-observed galaxies have had their distances systematically underestimated, by 0.1-0.3 mag in the distance modulus, due to the underappreciated influence of stellar profile blending on the WFC chips. The signature of such an effect would be a systematic trend in (i) the Type Ia supernovae corrected peak luminosity and (ii) the Tully-Fisher residuals, with increasing calibrator distance, and (iii) a differential offset between PC and WFC distance moduli, within the same galaxy. The absence of a trend would be expected if blending were negligible (as has been inherently assumed in the analyses of the aforementioned teams). We adopt a functional form for the predicted influence of blending that is consistent with the models of Mochejska et al. and Stanek & Udalski, and demonstrate that the expected correlation with distance predicted by these studies is not supported by the data. We conclude that the Cepheid-based extragalactic distance scale has not been severely compromised by the neglect of blending.Comment: 14 pages, 2 figures, 1 table, LaTeX, accepted for publication in Astrophysical Journal Letters, also available at http://casa.colorado.edu/~bgibson/publications.htm

非季節性熱帯雨林における一斉開花現象 : サラワク低地フタバガキ林における植物繁殖フェノロジーと植物-送粉者相互作用

本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである京都大学0048新制・課程博士博士(理学)甲第7693号理博第2078号新制||理||1105(附属図書館)UT51-99-G287京都大学大学院理学研究科生物科学専攻(主査)教授 山村 則男, 教授 堀 道雄, 教授 浅野 透学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA

Detection of the Red Giant Branch Stars in M82 Using the Hubble Space Telescope

We present color-magnitude diagrams and luminosity functions of stars in two halo regions of the irregular galaxy in M82, based on F555W and F814W photometry taken with the Hubble Space Telescope and Wide Field Planetary Camera 2. The I-band luminosity function shows a sudden jump at I~23.95 mag, which is identified as the tip of the red giant branch (TRGB). Adopting the Lee et al. (1993) calibration of the TRGB based on the RR Lyrae distances to Galactic globular clusters, we obtain the distance modulus of (m-M)_0=27.95 +- 0.14 (random) +- 0.16 (systematic) mag. This corresponds to a linear distance of 3.9 +- 0.3 (random) +- 0.3 (systematicf) Mpc, which agrees well with the distance of M81 deteremined from the HST observations of the Cepheid variable stars. In addition, we observe a significant number of stars apparently brighter than the TRGB. However, with the current data, we cannot rule out whether these stars are blends of fainter stars, or are indeed intermediate-age asymptotic giant branch stars.Comment: 8 figure

Heterostyly: speciation within a species

Almost all organisms in nature show nonrandom mating to different degrees. Two extreme results of nonrandom mating are speciation and sexual differentiation. Heterostyly is a form of sexual differentiation considered to have evolved to resolve conflicts between male and female functions of hermaphrodite flowers. Our study examines necessary and sufficient conditions for establishment of heterostyly using a configuration individual-based model. Previous models assume invasion of a mutant phenotype into a population with monomorphic wild phenotype. In contrast, our model demonstrates that heterostyly can be established from a population with continuous phenotypic variation, a proposition that requires simpler assumptions than the previous hypotheses. Results of our simulation show that genetic linkage between stigma and anther heights is essential for establishment of heterostyly. Dominance effects on the genes for stamen or stigma heights are not necessary, but they promote evolution of heterostyly. Probability of evolution of heterostyly also depends on the functional relationship between stigma–anther distance and strength of sexual interference, and the distance and probability of pollen deposition success. Parallelity and difference between speciation and sexual differentiation are also discussed

Precipitant-Free Crystallization of Lysozyme and Glucose Isomerase by Drying

Protein crystallization is usually conducted by using precipitants, although the “salting-out” phenomenon is still unclear and complex. Moreover, the addition of precipitants sometimes results in irreversible disordered precipitation of protein molecules. Although precipitant-free lysozyme crystals obtained by centrifugal concentration showed significant changes in three-dimensional structure compared to the structure of salted-out crystals, it was rather difficult to mount crystals from a viscous dense liquid phase after centrifugal concentration, and the quality of the crystals often deteriorated during the mounting process. Here we present novel precipitant-free crystallization methods, which were effective for lysozyme and glucose isomerase. Tetragonal lysozyme crystals were successfully crystallized in a glass capillary simply by drying highly concentrated lysozyme solution in the presence of 0.01 M hydrochloric acid without using any precipitants. Glucose isomerase dissolved in ultra-pure water was also successfully crystallized in hanging drops by drying highly concentrated solution under low-humidity conditions. Oscillation images of the obtained crystals were safely collected without handling; they clearly indicated the crystals had a tetragonal form for lysozyme and an orthorhombic form for glucose isomerase, and their lattice parameters are similar to those of previously reported crystals obtained by salting-out methods

Rapid modification of antibodies on the surface of liposomes composed of high-affinity protein A-conjugated phospholipid for selective drug delivery

Antibody-modified liposomes, immuno-liposomes, can selectively deliver encapsulated drug ‘cargos’ to cells via the interaction of cell surface proteins with antibodies. However, chemical modification of both the antibodies and phospholipids is required for the preparation of immuno-liposomes for each target protein using conventional methods, which is time-consuming. In the present study, we demonstrated that high-affinity protein A- (Protein A-R28: PAR28) displaying liposomes prepared by the post-insertion of PAR28-conjugated phospholipid through polyethylene glycol (PEG)-linkers (PAR28-PEG-lipo) can undergo rapid modification of antibodies on their surface, and the liposomes can be delivered to cells based on their modified antibodies. Anti-CD147 and anti-CD31 antibodies could be modified with PAR28-PEG-lipo within 1 h, and each liposome was specifically taken up by CD147- and CD31-positive cells, respectively. The cellular amounts of doxorubicin delivered by anti-CD147 antibody-modified PAR28-PEG-lipo were significantly higher than those of isotype control antibody-modified liposomes. PAR28-PEG-lipo can easily and rapidly undergo modification of various antibodies on their surface, which then makes them capable of selective drug delivery dependent on the antibodies

Infrared Spectra of the Subluminous Type Ia Supernova SN 1999by

Near-infrared (NIR) spectra of the subluminous Type Ia supernova SN 1999by are presented that cover the time evolution from about 4 days before to 2 weeks after maximum light. Analysis of these data was accomplished through the construction of an extended set of delayed detonation (DD) models covering the entire range of normal to subluminous SNe Ia. The explosion, light curves, and time evolution of the synthetic spectra were calculated self-consistently for each model, with the only free parameters being the initial structure of the white dwarf and the description of the nuclear burning front during the explosion. From these, one model was selected for SN 1999by by matching the synthetic and observed optical light curves, principally the rapid brightness decline. DD models require a minimum amount of burning during the deflagration phase, which implies a lower limit for the 56Ni mass of about 0.1 M☉ and consequently a lower limit for the SN brightness. The models that best match the optical light curve of SN 1999by were those with a 56Ni production close to this theoretical minimum. The data are consistent with little or no interstellar reddening [E(B-V) ≤ 0.12 mag], and we derive a distance of 11 ± 2.5 Mpc for SN 1999by, in agreement with other estimates. Without any modification, the synthetic spectra from this subluminous model match reasonably well the observed IR spectra taken on 1999 May 6, 10, 16, and 24. These dates correspond roughly to -4, 0, 6, and 14 days after maximum light. Prior to maximum, the NIR spectra of SN 1999by are dominated by products of explosive carbon burning (O, Mg) and Si. Spectra taken after maximum light are dominated by products of incomplete Si burning. Unlike the behavior of normal Type Ia SNe, lines from iron-group elements begin to show up only in our last spectrum taken about 2 weeks after maximum light. The implied distribution of elements in velocity space agrees well with the DD model predictions for a subluminous SN Ia. Regardless of the explosion model, the long duration of the phases dominated by layers of explosive carbon and oxygen burning argues that SN 1999by was the explosion of a white dwarf at or near the Chandrasekhar mass. The good agreement between the observations and the models without fine-tuning a large number of free parameters suggests that DD models are a good description of at least subluminous Type Ia SNe. Pure deflagration scenarios or mergers are unlikely, and helium-triggered explosions can be ruled out. However, problems for DD models still remain, since the data seem to be at odds with recent three-dimensional models of the deflagration phase that predict significant mixing of the inner layers of the white dwarf prior to detonation. Possible solutions include the effects of rapid rotation on the propagation of nuclear flames during the explosive phase of burning or extensive burning of carbon just prior to the runaway

Cepheid and Tip of the Red Giant Branch Distances To the Dwarf Irregular Galaxy IC10

We present color-magnitude diagrams and luminosity functions of stars in the nearby galaxy IC 10, based on VI CCD photometry acquired with the COSMIC prime-focus camera on the Palomar 5m telescope. The apparent I-band luminosity function of stars in the halo of IC 10 shows an identifiable rise at I~21.7 mag. This is interpreted as being the tip of the red giant branch (TRGB) at M_V~-4 mag. Since IC 10 is at a very low Galactic latitude, its foreground extinction is expected to be high and the uncertainty associated with that correction is the largest contributor to the error associated with its distance determination. Multi-wavelength observations of Cepheid variable stars in IC 10 give a Population I distance modulus of 24.1 +- 0.2 mag, which corresponds to a linear distance of 660 +- 66 kpc for a total line-of-sight reddening of E(B-V) = 1.16 +- 0.08 mag, derived self-consistently from the Cepheid data alone. Applying this Population I reddening to the Population II halo stars gives a TRGB distance modulus of 23.5 +- 0.2 mag, corresponding to 500 +- 50 kpc. We consider this to be a lower limit on the TRGB distance. Reconciling the Cepheid and TRGB distances would require that the reddening to the halo is $\Delta$E(B-V) = 0.31 mag lower than that into the main body of the galaxy. This then suggests that the Galactic extinction in the direction of IC10 is (B-V) ~ 0.85