543 research outputs found

    The effects of the spontaneous presence of a spouse/partner and others on cardiovascular reactions to an acute psychological challenge

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    The presence of supportive others has been associated with attenuated cardiovascular reactivity in the laboratory. The effects of the presence of a spouse and others in a more naturalistic setting have received little attention. Blood pressure and heart rate reactions to mental stress were recorded at home in 1028 married/partnered individuals. For 112 participants, their spouse/partner was present; for 78, at least one other person was present. Women tested with a spouse/partner present showed lower magnitude systolic blood pressure and heart rate reactivity than those tested without. Individuals tested with at least one nonspousal other present also displayed attenuated reactivity. This extends the results of laboratory studies and indicates that the spontaneous presence of others is associated with a reduction in cardiovascular reactivity in an everyday environment; spouse/partner presence would appear to be especially effective for women.\ud \u

    Herschel/HIFI Spectral Mapping of C+^+, CH+^+, and CH in Orion BN/KL: The Prevailing Role of Ultraviolet Irradiation in CH+^+ Formation

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    The CH+^+ ion is a key species in the initial steps of interstellar carbon chemistry. Its formation in diverse environments where it is observed is not well understood, however, because the main production pathway is so endothermic (4280 K) that it is unlikely to proceed at the typical temperatures of molecular clouds. We investigation CH+^+ formation with the first velocity-resolved spectral mapping of the CH+^+ J=10,21J=1-0, 2-1 rotational transitions, three sets of CH Λ\Lambda-doubled triplet lines, 12^{12}C+^+ and 13^{13}C+^+, and CH3_3OH 835~GHz E-symmetry Q branch transitions, obtained with Herschel/HIFI over \approx12 arcmin2^2 centered on the Orion BN/KL source. We present the spatial morphologies and kinematics, cloud boundary conditions, excitation temperatures, column densities, and 12^{12}C+^+ optical depths. Emission from C+^+, CH+^+, and CH is indicated to arise in the diluted gas, outside of the explosive, dense BN/KL outflow. Our models show that UV-irradiation provides favorable conditions for steady-state production of CH+^+ in this environment. Surprisingly, no spatial or kinematic correspondences of these species are found with H2_2 S(1) emission tracing shocked gas in the outflow. We propose that C+^+ is being consumed by rapid production of CO to explain the lack of C+^+ and CH+^+ in the outflow, and that fluorescence provides the reservoir of H2_2 excited to higher ro-vibrational and rotational levels. Hence, in star-forming environments containing sources of shocks and strong UV radiation, a description of CH+^+ formation and excitation conditions is incomplete without including the important --- possibly dominant --- role of UV irradiation.Comment: Accepted for publication in The Astrophysical Journa

    Evolutionary Status of Dwarf ``Transition'' Galaxies

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    We present deep B, R and Halpha imaging of 3 dwarf galaxies: NGC3377A, NGC4286, and IC3475. Based on previous broadband imaging and HI studies, these mixed-morphology galaxies were proposed by Sandage & Hoffman (1991) to be, respectively, a gas-rich low surface brightness Im dwarf, a nucleated dwarf that has lost most of its gas and is in transition from Im to dS0,N, and the prototypical example of a gas-poor ``huge low surface brightness'' early-type galaxy. From the combination of our broadband and Halpha imaging with the published information on the neutral gas content of these three galaxies, we find that (1) NGC3377A is a dwarf spiral; (2) NGC3377A and NGC4286 have comparable amounts of ongoing star formation, as indicated by their Halpha emission, while IC3475 has no detected HII regions to a very low limit; (3) the global star formation rates are at least a factor of 20 below that of 30 Doradus for NGC3377A and NGC4286; (4) while the amount of star formation is comparable, the distribution of star forming regions is very different between NGC3377A and NGC4286; (5) given their current star formation rates and gas contents, both NGC3377A and NGC4286 can continue to form stars for more than a Hubble time; (6) both NGC3377A and NGC4286 have integrated total B-R colors that are redder than the integrated total B-R color for IC3475, and thus it is unlikely that either galaxy will ever evolve into an IC3475 counterpart; and (7) IC3475 is too blue to be a dE. We thus conclude that we have not identified potential precursors to galaxies such as IC3475, and unless signifcant changes occur in the star formation rates, neither NGC3377A nor NGC4286 will evolve into a dwarf elliptical or dwarf spheroidal within a Hubble time.Comment: 34 pages, 6 jpg figures, 3 postscript figures, and 4 tables, uses AASTeX, ApJ, in pres

    LEDA 074886: A remarkable rectangular-looking galaxy

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    We report the discovery of an interesting and rare, rectangular-shaped galaxy. At a distance of 21 Mpc, the dwarf galaxy LEDA 074886 has an absolute R-band magnitude of -17.3 mag. Adding to this galaxy's intrigue is the presence of an embedded, edge-on stellar disk (of extent 2R_{e,disk} = 12 arcsec = 1.2 kpc) for which Forbes et al. reported V_rot/sigma ~ 1.4. We speculate that this galaxy may be the remnant of two (nearly edge-one) merged disk galaxies in which the initial gas was driven inward and subsequently formed the inner disk, while the stars at larger radii effectively experienced a dissipationless merger event resulting in this `emerald cut galaxy' having very boxy isophotes with a_4/a = -0.05 to -0.08 from 3 to 5 kpc. This galaxy suggests that knowledge from simulations of both `wet' and `dry' galaxy mergers may need to be combined to properly understand the various paths that galaxy evolution can take, with a particular relevance to blue elliptical galaxies.Comment: To appear in ApJ. Six pages including references and figure

    An Imaging Survey of Early-Type Barred Galaxies

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    This paper presents the results of a high-resolution imaging survey, using both ground-based and Hubble Space Telescope images, of a complete sample of nearby barred S0--Sa galaxies in the field, with a particular emphasis on identifying and measuring central structures within the bars: secondary bars, inner disks, nuclear rings and spirals, and off-plane dust. A discussion of the frequency and statistical properties of the various types of inner structures has already been published. Here, we present the data for the individual galaxies and measurements of their bars and inner structures. We set out the methods we use to find and measure these structures, and how we discriminate between them. In particular, we discuss some of the deficiencies of ellipse fitting of the isophotes, which by itself cannot always distinguish between bars, rings, spirals, and dust, and which can produce erroneous measurements of bar sizes and orientations.Comment: LaTeX, 66 pages (including 42 figures, 36 in color). To appear in The Astrophysical Journal Supplement. Full-resolution and text-only versions available at http://www.iac.es/galeria/erwin/research

    Detection of Compact Nuclear X-Ray Emission in NGC 4736

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    We report the results from a deep ROSAT PSPC observation of LINER galaxy NGC 4736. Two bright sources are detected, separated by only about 1', with the brighter one coinciding with the center of the galaxy. Neither source shows apparent X-ray variability on time-scales of minutes to hours in the ROSAT band. Simple power-law models, typical of AGN X-ray spectra, produce poor fits to the observed X-ray spectrum of the nuclear source. The addition of a Raymond-Smith component improves the fits significantly. This is consistent with the presence of hot gas in the nuclear region with kT=~0.3 keV, in addition to a compact nuclear source. However, a careful examination of the residuals reveal apparent features at low energies (< 0.25 keV). We find that the addition of a narrow emission line at about 0.22 keV is a significant improvement to the parameterization of the spectrum. We examine the results in the light of the accuracy of the PSPC spectral calibration. The derived photon index is about 2.3, which is similar to those for Seyfert 1 galaxies measured in the ROSAT energy range. On the other hand, the 0.1-2 keV luminosity for the compact source is only about 3.4x10^{39} erg/s, much fainter than typical Seyfert galaxies. We discuss the implications of these results on the connection between LINERs and AGNs. The off-center source is transient in nature. It has a hard X-ray spectrum, with a photon index of about 1.5, so is likely to be an X-ray binary. There is still some ambiguity regarding its association with the galaxy. If it is indeed located in the galaxy, the 0.1-2 keV luminosity would be greater than 5.1x10^{38} erg/s, making it a stellar-mass black hole candidate.Comment: 15 pages, LaTeX (aaspp4.sty), macro rotate.tex, 10 postscript figures (including 3 color prints) and rotate.tex available at ftp://space.mit.edu/pub/cui/ngc4736/ . Accepted for publication in Ap

    The Frequency of Barred Spiral Galaxies in the Near-IR

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    We have determined the fraction of barred galaxies in the H-band for a statistically well-defined sample of 186 spirals drawn from the Ohio State University Bright Spiral Galaxy survey. We find 56% of our sample to be strongly barred at H, while another 16% is weakly barred. Only 27% of our sample is unbarred in the near-infrared. The RC3 and the Carnegie Atlas of Galaxies both classify only about 30% of our sample as strongly barred. Thus strong bars are nearly twice as prevalent in the near-infrared as in the optical. The frequency of genuine optically hidden bars is significant, but lower than many claims in the literature: 40% of the galaxies in our sample that are classified as unbarred in the RC3 show evidence for a bar in the H-band, while for the Carnegie Atlas this fraction is 66%. Our data reveal no significant trend in bar fraction as a function of morphology in either the optical or H-band. Optical surveys of high redshift galaxies may be strongly biased against finding bars, as bars are increasingly difficult to detect at bluer rest wavelengths.Comment: LaTeX with AASTeX style file, 23 pages with 6 figures. Accepted for publication in The Astronomical Journal (Feb. 2000

    H-alpha Kinematics of the SINGS Nearby Galaxies Survey. II

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    This is the second part of an H-alpha kinematics follow-up survey of the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample. The aim of this program is to shed new light on the role of baryons and their kinematics and on the dark/luminous matter relation in the star forming regions of galaxies, in relation with studies at other wavelengths. The data for 37 galaxies are presented. The observations were made using Fabry-Perot interferometry with the photon-counting camera FaNTOmM on 4 different telescopes, namely the Canada-France-Hawaii 3.6m, the ESO La Silla 3.6m, the William Herschel 4.2m, and the Observatoire du mont Megantic 1.6m telescopes. The velocity fields are computed using custom IDL routines designed for an optimal use of the data. The kinematical parameters and rotation curves are derived using the GIPSY software. It is shown that non-circular motions associated with galactic bars affect the kinematical parameters fitting and the velocity gradient of the rotation curves. This leads to incorrect determinations of the baryonic and dark matter distributions in the mass models derived from those rotation curves.Comment: 18 pages, 5 figures, 4 tables. Accepted for publication in MNRAS. All high-res. figures are available at http://www.astro.umontreal.ca/fantomm/singsII
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