the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in © 2018. This approach is illustrated using recent Coma Cluster distance data, together with recent Hipparcos data for RR Lyrae stars.
However, determining ages from the colours of galaxies is a relatively crude method that is subject to large uncertainties.
Read the very best research published in IOP journalsArticles from the past year selected by our editorsRead open access proceedings from science conferences worldwide
Image credits: Willis and colleagues’ galaxy cluster: N. A. Hatch; Coma cluster: Russ Carroll, Rob Gendler, Bob Franke/Dan Zowada Memorial Observatory, Wayne State Univ. A comparison of the spectra with models will be a much more accurate way to determine the ages of the stars than using the colours of galaxies. The comparison is shown in Figure Two reference lines are shown for comparison with the cluster dwarfs. Unfortunately, observations of this era are challenging because dark-age galaxies are exceptionally faintA galaxy cluster is a group of thousands of galaxies that orbit each other at speedsAlthough nearby clusters, such as the Coma cluster, are easier to observe than those farther away, we cannot measure their ages precisely because the galaxies are extremely old. The core is dominated by two giant cD ellipticals NGC4889 and NGC4874. and V-band photometry of 101 galaxies in the Coma cluster, to investigate how mean age and metal abundance correlate with galaxy luminosity. Among F and G dwarf stars in open clusters of age comparable to the Hyades (~600 Myr) the levels of chromospheric and coronal activity have been well studied (Skumanich The youngest cluster in this study is one that has received much less attention than either the Hyades or Coma Ber. Thank you for visiting nature.com. Whereas these other two clusters are within ~100 pc of the Sun, NGC 2281 is some five times further away. (2002) find a gradient in the Mg 2 and Fe indices, which they attribute to pressure confinement of the supernova ejecta by the ICM (Pasquali et al., 2012, also). The Coma Cluster of Galaxies contains about 1000 galaxies in an area of roughly 3x5 degrees on the sky, of which the central part is shown in the full field.
This paper presents a way of finding mutually consistent values of Omega_M, t_0, and H_0. To find out more, see our Therefore, although the authors’ results are tantalizing, they should be treated with caution until NASA’s James Webb Space Telescope (JWST) is launched in the next few years.The JWST will measure spectra of the light emitted by these galaxies. By continuing to use this site you agree to our use of cookies. You are using a browser version with limited support for CSS. Although nearby clusters, such as the Coma cluster, are easier to observe than those farther away, we cannot measure their ages precisely because the galaxies are extremely old.
You do not need to reset your password if you login via Athens or an Institutional login.Click here to close this overlay, or press the "Escape" key on your keyboard.UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USAChromospheric activity among late-F, G, K dwarfs is known to vary with stellar age (e.g., Eggen The far-ultraviolet (FUV) brightness of late-F, G, and K dwarfs, as measured by the Late-type dwarf stars in open clusters of known age (derived, for example, from color–magnitude diagram studies) provide a potential for approaching the issue of FUV activity as a function of stellar age.
From isochrone fitting to the color–magnitude diagram, Odenkirchen et al.
Nina A. Hatch is in the School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK. is grateful for support from NASA grant NNX07AJ42G made through the The current data could be consistent with the slope of the upper main sequence becoming steeper with decreasing cluster age. Internet Explorer). Observations of a distant cluster of galaxies suggest that star formation began there only 370 million years after the Big Bang. For galaxies in the Coma cluster (z = 0.023), Carter et al. The solid line in Figure Both cluster main sequences are offset by some 0.5–1.5 mag in Figure The two-color loci of the dwarfs in all three clusters considered in this paper are compared in Figure The observed two-color diagram of the NGC 2281 dwarfs, by contrast, shows a substantial offset in Figure The effect of making the above two reddening corrections to the data for NGC 2281 is illustrated in Figure The consequences of uncertainties in the age and reddening determinations for NGC 2281 were further explored by using a tool within the WEBDA website that allows overplotting of both Padova (Girardi et al. Note that these fits relate the observed colors of the cluster dwarfs with no correction for reddening. The Astronomical Society of the Pacific. We find that the CMR in Coma is driven primarily by a luminosity–metallicity correlation.
If you have a user account, you will need to reset your password the next time you login. This site uses cookies. The results provide key details about where and when the first stars and galaxies emerged in the Universe.
All rights reserved.
In particular, we use the line index measurements to address the origin of the colour–magnitude relation (CMR). Enjoy millions of the latest Android apps, games, music, movies, TV, books, magazines & more. During these cosmic dark ages, which lasted for several hundred million years, the first stars and galaxies emerged. and JavaScript.Shortly after the Big Bang, the Universe was completely dark. Anytime, anywhere, across your devices. To obtain For example, in the case of the Coma Ber stars that were used to derive Equation (Given that the upper main sequences of the Hyades and Coma Ber open clusters follow reasonably well-defined loci in the (G.H.S. Stars and galaxies, which provide the Universe with light, had not yet formed, and the Universe consisted of a primordial soup of neutral hydrogen and helium atoms and invisible ‘dark matter’. As a result, galaxies that have red colours formed their stars a long time agoIn my opinion, Willis and colleagues’ age estimates are the best ones possible, given the limited data that the authors have from the Hubble telescope. You will only need to do this once. Their suggestion is loosely supported by the ram-pressure stripping (RPS) model of Gupta et al.