Tidal dwarfs in the M81 group: the second generation?     

L. Makarova  E. Grebel  I. Karachentsev  A. Dolphin  V. Karachentseva  M. Sharina  D. Geisler  P. Guhathakurta  P. Hodge  A. Sarajedini  P. Seitzer 《Astrophysics and Space Science》2003,285(1):107-111

We present a quantitative star formation history derivation of the four suspected tidal dwarf galaxies in the M 81 group: Holmberg IX, BK3N,Arp-loop (A0952+69) and Garland using HST/WFPC2 images of these galaxies. We construct a library of synthetic Colour-Magnitude Diagrams(CMDs) based on theoretical isochrones and data-derived determinations of photometric errors. These synthetic CMDs were combined linearly andχ²-compared to observed photometry. All the galaxies show continuous star formation between about 20 and 200 Myr ago with star formation rates between 7.5⋅10^-3 M_⊙/yr and 7.67⋅10^-4 M_⊙/yr. The metallicity of the detected stars is spanning rather a wide range, being lower than solar abundance. We suppose, that all the galaxies were formed out of material from metal-poor outer part of the giant spiral galaxy M81after tidal interaction about 200 Myr ago. However, this suggestion requires significantly more deep color-magnitude diagrams to be sure with the scenario of the galaxy evolution. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Book review     

P.W. Hodge  B.P. Skelton  J. Ashizawa 《Astrophysics and Space Science》2003,286(3-4):529-529

  相似文献   

Assessing infrequent large earthquakes using geomorphology and geodesy: the Malawi Rift     

Michael Hodge  Juliet Biggs  Katsuichiro Goda  Willy Aspinall 《Natural Hazards》2015,76(3):1781-1806

  相似文献   

Testing the Limits of ICP-MS: Determination of Trace Elements in Ground Water at the Part-Per-Trillion Level   总被引：3，自引：0，他引：3  

Klaus J. Stetzenbach  Megumi Amano  David K. Kreamer  Vernon F. Hodge 《Ground water》1994,32(6):976-985

  相似文献   

Pumping Effects of Wells in Fractured Granitic Terrain     

A. P. Kohut  J. C. Foweraker  D. A. Johanson  E. H. Tradewell  W. S. Hodge 《Ground water》1983,21(5):564-572

  相似文献   

A Controlled Field Test of Surfactant-Enhanced Aquifer Remediation   总被引：4，自引：0，他引：4  

John C. Fountain  Robert C. Starr  Thomas Middleton  Michael Beikirch  Craig Taylor  Dennis Hodge 《Ground water》1996,34(5):910-916

  相似文献   

U.S. Mussel Watch: 1977–1978 results on trace metals and radionuclides     

Edward D. Goldberg  Minoru Koide  Vern Hodge  A.Russel Flegal  John Martin 《Estuarine, Coastal and Shelf Science》1983,16(1):69-93

The results of the U.S. Mussel Watch Monitoring Program for the period 1976–1978 for trace metals and artificial radionuclides in bivalves are presented. The substances analysed included Ag, Cu, Zn, Cd, Ni, Pb, ²³⁸Pu, ^239+240Pu and ²⁴¹Am. The analyses of organic substances will be presented elsewhere. The concentrations of these substances in the bivalves may reflect upwelling processes, anthropogenic inputs or natural levels. Off the California coast, mussels show markedly elevated Pu and Cd concentrations in coastal areas adjacent to the most intensive upwelling zones. Elevated levels of Pb, for example, are found in organisms living adjacent to highly urbanized places. The general patterns of distribution repeat themselves year after year at a given site. Thus, it is concluded that annual monitoring activities may not be necessary and that a frequency of sampling of several or so years may be more appropriate to identify pollution problems. Finally, national or regional baselines for metal concentrations in bivalves from unpolluted waters are proposed. National baselines for Pb in the west coast mussels of 1·0 parts 10^?6 and for Ag in east coast mussels of 0·05 parts 10^?6 are suggested.  相似文献   

Lunar and terrestrial impact crater spherules     

P. W. Hodge 《Earth, Moon, and Planets》1973,7(3-4):483-486

Comparisons between the chemistry of impact debris, especially spherical droplets of impact-formed material, are made for lunar samples and for soil samples taken from terrestrial impact sites. Differences are assigned to differences in the chemistry of impacting bodies and in the surface rocks, and to the influence of the atmosphere in the terrestrial cases.Paper dedicated to Professor Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.  相似文献   

HST colour–magnitude diagrams of six old globular clusters in the LMC     

K. A. G. Olsen  P. W. Hodge  M. Mateo  E. W. Olszewski  R. A. Schommer  N. B. Suntzeff  & A. R. Walker 《Monthly notices of the Royal Astronomical Society》1998,300(3):665-685

We report on HST observations of six candidate old globular clusters in the Large Magellanic Cloud (LMC): NGC 1754, 1835, 1898, 1916, 2005 and 2019. Deep exposures with the F555W and F814W filters provide us with colour–magnitude diagrams that reach to an apparent magnitude in V of ∼25, well below the main-sequence turn-off. These particular clusters are associated with significantly high LMC field star densities and care was taken to subtract the field stars from the cluster colour–magnitude diagrams accurately. In two cases there is significant variable reddening across at least part of the image, but only for NGC 1916 does the differential reddening preclude accurate measurements of the CMD characteristics. The morphologies of the colour–magnitude diagrams match well those of Galactic globular clusters of similar metallicity. All six have well-developed horizontal branches, while four clearly have stars on both sides of the RR Lyrae gap. The abundances obtained from measurements of the height of the red giant branch above the level of the horizontal branch are 0.3 dex higher, on average, than previously measured spectroscopic abundances. Detailed comparisons with Galactic globular cluster fiducials show that all six clusters are old objects, very similar in age to classical Galactic globulars such as M5, with little age spread among the clusters. This result is consistent with ages derived by measuring the magnitude difference between the horizontal branch and main-sequence turn-off. We also find a similar chronology by comparing the horizontal branch morphologies and abundances with the horizontal branch evolutionary tracks of Lee, Demarque &38; Zinn. Our results imply that the LMC formed at the same time as the Milky Way Galaxy.  相似文献   

The stellar content of a spiral arm of NGC 4321     

Ted K. Wyder  rew E. Dolphin  & Paul W. Hodge 《Monthly notices of the Royal Astronomical Society》1998,298(1):259-266

The effects of the passage of a spiral arm through the disc of the giant Virgo Sc galaxy NGC 4321 are investigated with Hubble Space Telescope WFPC2 images in two colours. Concentrating on a portion of the southern spiral arm of NGC 4321, we have applied a new program to solve for the star formation histories in the arm and interarm regions separately. The observational uncertainties and the variable crowding across the spiral arm are taken into account using the results of artificial star tests. In the interarm regions the data are consistent with a constant star formation rate for the last 50 Myr while the stars in the arm region show a star formation rate four times larger than in the interarm regions in the last 5 Myr.  相似文献