Shoko Sakai

Nihon University

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Robert C. Kennicutt

University of Arizona

J. R. Mould

Swinburne University of Technology

Shaun M. G. Hughes

Washington University in St. Louis

J. P. Huchra

Center for Astrophysics Harvard & Smithsonian

Wendy L. Freedman

University of Chicago

G. D. Illingworth

University of California, Santa Cruz

P. B. Stetson

Herzberg Institute of Astrophysics

Laura Ferrarese

Herzberg Institute of Astrophysics

N. A. Silbermann

California Institute of Technology

J. A. Graham

Carnegie Institution for Science

Cooperative Institutions

University of Arizona

U.S. National Science Foundation

Kitt Peak National Observatory

Association of Universities For Research In Astronomy

Space Telescope Science Institute

California Institute of Technology

Max Planck Society

Carnegie Observatories

Max Planck Institute for Astronomy

Center for Astrophysics Harvard & Smithsonian

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

On the error boundary paralleogram of Ship's Positions

Nihon Kokai Gakkaishi/Nihon Kōkai Gakkaishi (1955)

Shoko Sakai Yukihiko Namikawa

The error parallelogram, ellipse and circle are considered to be the error boundary of ship's positions. We have made reseach about these three kinds of the error boundary theoretically and mathematically. The accuracy of the fix is shown by the area of the parallelogram, for this area is in inverse proportion to the probability density. So by drawning the curves of constant area we have got accuracy contour maps of ship's positions fixed by cross bearing and transfered position line method. The error of the estimated ship's position is discussed in Appendix II.

Parallelogram

Ellipse

Position (finance)

Constant (computer programming)

Line (geometry)

Quadrilateral

10.9749/jina.12.0_17

Cite

Citations (0)

DWARF GALAXY STARBURST STATISTICS IN THE LOCAL VOLUME

The Astrophysical Journal (2009)

Janice Lee Robert C. Kennicutt S. J. José G. Funes Shoko Sakai Sanae Akiyama

An unresolved question in galaxy evolution is whether the star formation histories of low mass systems are preferentially dominated by starbursts or modes that are more quiescent and continuous. Here, we quantify the prevalence of global starbursts in dwarf galaxies at the present epoch, and infer their characteristic durations and amplitudes. The analysis is based on the H-alpha component of the 11 Mpc H-alpha UV Galaxy Survey (11HUGS), which is providing H-alpha and GALEX UV imaging for an approximately volume-limited sample of ~300 star-forming galaxies within 11 Mpc. We first examine the completeness properties of the sample, and then directly tally the number of bursting dwarfs and compute the fraction of star formation that is concentrated in such systems. Our results are consistent with a picture where dwarfs that are currently experiencing massive global bursts are just the ~6% tip of a low-mass galaxy iceberg. Moreover, bursts are only responsible for about a quarter of the total star formation in the overall dwarf population, so the majority of stars in low-mass systems are not formed in this mode today. Spirals and irregulars devoid of H-alpha emission are rare, indicating that the complete cessation of star formation generally does not occur in such galaxies and is not characteristic of the inter-burst state, at least for the more luminous systems with M(B)<-15. The starburst statistics presented here directly constrain the duty cycle and the average burst amplitude under the simplest assumptions where all dwarf irregulars share a common star formation history and undergo similar bursts cycles with equal probability. Uncertainties in such assumptions are discussed in the context of previous work.

10.1088/0004-637x/692/2/1305

Cite

Citations (160)

THE CALIBRATION OF MONOCHROMATIC FAR-INFRARED STAR FORMATION RATE INDICATORS

The Astrophysical Journal (2010)

Daniela Calzetti S.-Y. Wu Sungryong Hong Robert C. Kennicutt Janice Lee

Spitzer data at 24, 70, and 160 μm and ground-based Hα images are analyzed for a sample of 189 nearby star-forming and starburst galaxies to investigate whether reliable star formation rate (SFR) indicators can be defined using the monochromatic infrared dust emission centered at 70 and 160 μm. We compare recently published recipes for SFR measures using combinations of the 24 μm and observed Hα luminosities with those using 24 μm luminosity alone. From these comparisons, we derive a reference SFR indicator for use in our analysis. Linear correlations between SFR and the 70 μm and 160 μm luminosity are found for L(70) ≳ 1.4 × 1042 erg s−1 and L(160) ≳ 2 × 1042 erg s−1, corresponding to SFR ≳ 0.1–0.3 M☉ yr−1, and calibrations of SFRs based on L(70) and L(160) are proposed. Below those two luminosity limits, the relation between SFR and 70 μm (160 μm) luminosity is nonlinear and SFR calibrations become problematic. A more important limitation is the dispersion of the data around the mean trend, which increases for increasing wavelength. The scatter of the 70 μm (160 μm) data around the mean is about 25% (factor ∼2) larger than the scatter of the 24 μm data. We interpret this increasing dispersion as an effect of the increasing contribution to the infrared emission of dust heated by stellar populations not associated with the current star formation. Thus, the 70 (160) μm luminosity can be reliably used to trace SFRs in large galaxy samples, but will be of limited utility for individual objects, with the exception of infrared-dominated galaxies. The nonlinear relation between SFR and the 70 and 160 μm emission at faint galaxy luminosities suggests a variety of mechanisms affecting the infrared emission for decreasing luminosity, such as increasing transparency of the interstellar medium, decreasing effective dust temperature, and decreasing filling factor of star-forming regions across the galaxy. In all cases, the calibrations hold for galaxies with oxygen abundance higher than roughly 12 +log(O/H) ∼ 8.1. At lower metallicity, the infrared luminosity no longer reliably traces the SFR because galaxies are less dusty and more transparent.

Monochromatic color

Star (game theory)

10.1088/0004-637x/714/2/1256

Cite

Citations (322)

Advanced Camera for Surveys Imaging of 25 Galaxies in Nearby Groups and in the Field

The Astronomical Journal (2006)

И. Д. Караченцев Andrew E. Dolphin R. Brent Tully М. Е. Шарина Л. Н. Макарова

We present Hubble Space Telescope Advanced Camera for Surveys images and color-magnitude diagrams for 25 nearby galaxies with radial velocities VLG < 500 km s-1. Distances are determined based on the luminosities of stars at the tip of the red giant branch that range from 2 to 12 Mpc. Two of the galaxies, NGC 4163 and IC 4662, are found to be the nearest known representatives of blue compact dwarf objects. Using high-quality data on distances and radial velocities of 110 nearby field galaxies, we derive their mean Hubble ratio to be 68 km s-1 Mpc-1 with a standard deviation of 15 km s-1 Mpc-1. Peculiar velocities of most of the galaxies, Vpec = VLG - 68D, follow a Gaussian distribution with σv = 63 km s-1 but with a tail toward high negative values. Our data display the known correlation between peculiar velocity and galaxy elevation above the Local Supercluster plane. The small observed fraction of galaxies with high peculiar velocities, Vpec < -500 km s-1, may be understood as objects associated with nearby groups (Coma I, Eridanus) outside the local volume.

Local Group

Supercluster (genetic)

Red-giant branch

Coma Cluster

10.1086/500013

Cite

Citations (132)

The Hubble Space Telescope Extragalactic Distance Scale Key Project: The Discovery of Cepheids in NGC 2090

American Astronomical Society Meeting Abstracts (1996)

Shoko Sakai Randy L. Phelps Wendy L. Freedman Barry F. Madore A. Saha

Cosmic distance ladder

Hubble sequence

Source

Cite

Citations (0)

TheHubble Space TelescopeExtragalactic Distance Scale Key Project. VII. The Discovery of Cepheids in the Leo I Group Galaxy NGC 3351

The Astrophysical Journal (1997)

J. A. Graham Randy L. Phelps Wendy L. Freedman Abhijit Saha Laura Ferrarese

We report of the discovery and properties of Cepheid variable stars in the barred spiral galaxy NGC 3351 which is a member of the Leo I group of galaxies. NGC 3351 is one of 18 galaxies being observed as part of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale which aims to determine the Hubble constant to 10% accuracy. Our analysis is based on observations made with the Wide Field Planetary Camera 2 during 1994 and early 1995. The Leo I group contains several bright galaxies of diverse types and is very suitable for linking together a number of secondary calibrators which can be employed at much greater distances than the Cepheid variables. We identify 49 probable Cepheids within NGC 3351 in the period range 10-43 days which have been observed at 12 epochs with the F555W filter and 4 epochs using the F814W filter. The HST F555W and F814W data have been transformed to the Johnson V and Cousins I magnitude systems, respectively. Photometry has principally been carried out using the DAOPHOT/ALLFRAME package. Reference is made to parallel measurements being made with the DoPHOT package.

Cosmic distance ladder

Local Group

Hubble sequence

10.1086/303740

Cite

Citations (80)

The HST Key Project on the Extragalactic Distance Scale XX. The Discovery of Cepheids in the Virgo Cluster Galaxy NGC 4548

The Astrophysical Journal (1998)

J. A. Graham Laura Ferrarese Wendy L. Freedman R. C. Kennicutt J. R. Mould

This is one of the galaxies being observed as part of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale which aims to determine the Hubble Constant to 10% accuracy.

Virgo Cluster

Cosmic distance ladder

Hubble sequence

Source

Cite

Citations (0)

A Database of Cepheid Distance Moduli and TRGB, GCLF, PNLF and SBF Data Useful for Distance Determinations

arXiv (Cornell University) (1999)

Laura Ferrarese H. C. Ford J. P. Huchra Robert C. Kennicutt J. R. Mould

We present a compilation of Cepheid distance moduli and data for four secondary distance indicators that employ stars in the old stellar populations: the planetary nebula luminosity function (PNLF), the globular cluster luminosity function (GCLF), the tip of the red giant branch (TRGB), and the surface brightness fluctuation (SBF) method. The database includes all data published as of July 15, 1999. The main strength of this compilation resides in all data being on a consistent and homogeneous system: all Cepheid distances are derived using the same calibration of the period-luminosity relation, the treatment of errors is consistent for all indicators, measurements which are not considered reliable are excluded. As such, the database is ideal for inter-comparing any of the distance indicators considered, or for deriving a Cepheid calibration to any secondary distance indicator. Specifically, the database includes: 1) Cepheid distances, extinctions and metallicities; 2) apparent magnitudes of the PNLF cutoff; 3) apparent magnitudes and colors of the turnover of the GCLF (both in the V- and B-bands); 4) apparent magnitudes of the TRGB (in the I-band) and V-I colors at and 0.5 magnitudes fainter than the TRGB; 5) apparent surface brightness fluctuation magnitudes I, K', K_short, and using the F814W filter with the HST/WFPC2. In addition, for every galaxy in the database we give reddening estimates from DIRBE/IRAS as well as HI maps, J2000 coordinates, Hubble and T-type morphological classification, apparent total magnitude in B, and systemic velocity. (Abridged)

Cosmic distance ladder

Distance modulus

Absolute magnitude

Surface brightness fluctuation

Source

Cite

Citations (124)

The HST Key Project on the Extragalactic Distance Scale

The Astrophysical Journal (1998)

Laura Ferrarese Fabio Bresolin Robert C. Kennicutt Abhijit Saha P. B. Stetson

We report the detection of Cepheids and a new distance to the spiral galaxy NGC 2541, based on data obtained with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope (HST).

Cosmic distance ladder

Hubble sequence

Source

Cite

Citations (3)

A GALEX ULTRAVIOLET IMAGING SURVEY OF GALAXIES IN THE LOCAL VOLUME

The Astrophysical Journal Supplement Series (2010)

Janice Lee A. Gil de Paz Robert C. Kennicutt M. S. Bothwell Julianne J. Dalcanton

We present results from a GALEX ultraviolet (UV) survey of a complete sample of 390 galaxies within ∼11 Mpc of the Milky Way. The UV data are a key component of the composite Local Volume Legacy, an ultraviolet-to-infrared imaging program designed to provide an inventory of dust and star formation in nearby spiral and irregular galaxies. The ensemble data set is an especially valuable resource for studying star formation in dwarf galaxies, which comprise over 80% of the sample. We describe the GALEX survey programs that obtained the data and provide a catalog of far-UV (∼1500 Å) and near-UV (∼2200 Å) integrated photometry. General UV properties of the sample are briefly discussed. We compute two measures of the global star formation efficiency, the star formation rate (SFR) per unit H i gas mass, and the SFR per unit stellar mass, to illustrate the significant differences that can arise in our understanding of dwarf galaxies when the FUV is used to measure the SFR instead of Hα. We find that dwarf galaxies may not be as drastically inefficient in converting gas into stars as suggested by prior Hα studies. In this context, we also examine the UV properties of late-type dwarf galaxies that appear to be devoid of star formation because they were not detected in previous Hα narrowband observations. Nearly all such galaxies in our sample are detected in the FUV and have FUV SFRs that fall below the limit where the Hα flux is robust to Poisson fluctuations in the formation of massive stars. Otherwise, the UV colors and star formation efficiencies of Hα-undetected, UV-bright dwarf irregulars appear to be relatively unremarkable with respect to those exhibited by the general population of star-forming galaxies.

Ultraviolet

Stellar mass

10.1088/0067-0049/192/1/6

Cite

Citations (210)