http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
ARRAKIS: atlas of resonance rings as known in the S<sup>4</sup>G
Comeró,n, S.,Salo, H.,Laurikainen, E.,Knapen, J. H.,Buta, R. J.,Herrera-Endoqui, M.,Laine, J.,Holwerda, B. W.,Sheth, K.,Regan, M. W.,Hinz, J. L.,Muñ,oz-Mateos, J. C.,Gil de Paz, A.,Men&eac Springer-Verlag 2014 Astronomy and astrophysics Vol.562 No.-
<P>Context. Resonance rings and pseudorings (here collectively called rings) are thought to be related to the gathering of material near dynamical resonances caused by non-axisymmetries in galaxy discs. This means that they are the result of secular evolution processes that redistribute material and angular momentum in discs. Studying them may give clues on the formation and growth of bars and other disc non-axisymmetries. Aims. Our aims are to produce a catalogue and an atlas of the rings detected in the Spitzer Survey of Stellar Structure in Galaxies (S<SUP>4</SUP>G) and to conduct a statistical study of the data in the catalogue. Methods. We traced the contours of rings previously identified and fitted them with ellipses. We found the orientation of bars by studying the galaxy ellipse fits from the S<SUP>4</SUP>G pipeline 4. We used the galaxy orientation data obtained by the S<SUP>4</SUP>G pipeline 4 to obtain intrinsic ellipticities and orientations of rings and the bars. Results. ARRAKIS contains data on 724 ringed galaxies in the S<SUP>4</SUP>G. The frequency of resonance rings in the S<SUP>4</SUP>G is of 16 ±1% and 35 ±1% for outer and inner features, respectively. Outer rings are mostly found in Hubble stages −1 ≤T≤ 4. Inner rings are found in a broad distribution that covers the range −1 ≤T≤7. We confirm that outer rings have two preferred orientations, namely parallel and perpendicular to the bar. We confirm a tendency for inner rings to be oriented parallel to the bar, but we report the existence of a significant fraction (maybe as large as 50%) of inner features that have random orientations with respect to the bar. These misaligned inner rings are mostly found in late-type galaxies (T ≥4). We find that the fraction of barred galaxies hosting outer (inner) rings is ~1.7 times (~1.3 times) that in unbarred galaxies. Conclusions. We confirm several results from previous surveys as well as predictions from simulations of resonant rings and/or from manifold flux tube theory. We report that a significant fraction of inner rings in late-type galaxies have a random orientation with respect to the bar. This may be caused by spiral modes that are decoupled from the bar and dominate the Fourier amplitude spectrum at the radius of the inner ring. The fact that rings are only mildly favoured by bars suggests that those in unbarred galaxies either formed because of weak departures from the axisymmetry of the galactic potential or that they are born because of bars that were destroyed after the ring formation.</P>
Comeró,n, Sé,bastien,Elmegreen, Bruce G.,Salo, Heikki,Laurikainen, Eija,Athanassoula, E.,Bosma, Albert,Knapen, Johan H.,Gadotti, Dimitri A.,Sheth, Kartik,Hinz, Joannah L.,Regan, Michael W. IOP Publishing 2012 The Astrophysical journal Vol.759 No.2
<P>Breaks in the radial luminosity profiles of galaxies have until now been mostly studied averaged over disks. Here, we study separately breaks in thin and thick disks in 70 edge-on galaxies using imaging from the Spitzer Survey of Stellar Structure in Galaxies. We built luminosity profiles of the thin and thick disks parallel to midplanes and we found that thin disks often truncate (77%). Thick disks truncate less often (31%), but when they do, their break radius is comparable with that in the thin disk. This suggests either two different truncation mechanisms-one of dynamical origin affecting both disks simultaneously and another one only affecting the thin disk-or a single mechanism that creates a truncation in one disk or in both depending on some galaxy property. Thin disks apparently antitruncate in around 40% of galaxies. However, in many cases, these antitruncations are an artifact caused by the superposition of a thin disk and a thick disk, with the latter having a longer scale length. We estimate the real thin disk antitruncation fraction to be less than 15%. We found that the ratio of the thick and thin stellar disk mass is roughly constant (0.2 < M-T/M-t < 0.7) for circular velocities v(c) > 120 km s(-1), but becomes much larger at smaller velocities. We hypothesize that this is due to a combination of a high efficiency of supernova feedback and a slower dynamical evolution in lower-mass galaxies causing stellar thin disks to be younger and less massive than in higher-mass galaxies.</P>
Meidt, Sharon E.,Schinnerer, Eva,Knapen, Johan H.,Bosma, Albert,Athanassoula, E.,Sheth, Kartik,Buta, Ronald J.,Zaritsky, Dennis,Laurikainen, Eija,Elmegreen, Debra,Elmegreen, Bruce G.,Gadotti, Dimitri IOP Publishing 2012 The Astrophysical journal Vol.744 No.1
<P>With the aim of constructing accurate two-dimensional maps of the stellar mass distribution in nearby galaxies from Spitzer Survey of Stellar Structure in Galaxies 3.6 and 4.5 mu m images, we report on the separation of the light from old stars from the emission contributed by contaminants. Results for a small sample of six disk galaxies (NGC 1566, NGC 2976, NGC 3031, NGC 3184, NGC 4321, and NGC 5194) with a range of morphological properties, dust content, and star formation histories are presented to demonstrate our approach. To isolate the old stellar light from contaminant emission (e.g., hot dust and the 3.3 mu m polycyclic aromatic hydrocarbon (PAH) feature) in the IRAC 3.6 and 4.5 mu m bands we use an independent component analysis (ICA) technique designed to separate statistically independent source distributions, maximizing the distinction in the [3.6]-[4.5] colors of the sources. The technique also removes emission from evolved red objects with a low mass-to-light ratio, such as asymptotic giant branch (AGB) and red supergiant (RSG) stars, revealing maps of the underlying old distribution of light with [3.6]-[4.5] colors consistent with the colors of K and M giants. The contaminants are studied by comparison with the non-stellar emission imaged at 8 mu m, which is dominated by the broad PAH feature. Using the measured 3.6 mu m/8 mu m ratio to select individual contaminants, we find that hot dust and PAHs together contribute between similar to 5% and 15% to the integrated light at 3.6 mu m, while light from regions dominated by intermediate-age (AGB and RSG) stars accounts for only 1%-5%. Locally, however, the contribution from either contaminant can reach much higher levels; dust contributes on average 22% to the emission in star-forming regions throughout the sample, while intermediate-age stars contribute upward of 50% in localized knots. The removal of these contaminants with ICA leaves maps of the old stellar disk that retain a high degree of structural information and are ideally suited for tracing stellar mass, as will be the focus in a companion paper.</P>
Comeró,n, Sé,bastien,Elmegreen, Bruce G.,Knapen, Johan H.,Salo, Heikki,Laurikainen, Eija,Laine, Jarkko,Athanassoula, E.,Bosma, Albert,Sheth, Kartik,Regan, Michael W.,Hinz, Joannah L.,de Pa IOP Publishing 2011 The Astrophysical journal Vol.741 No.1
<P>Most, if not all, disk galaxies have a thin (classical) disk and a thick disk. In most models thick disks are thought to be a necessary consequence of the disk formation and/or evolution of the galaxy. We present the results of a study of the thick disk properties in a sample of carefully selected edge-on galaxies with types ranging from T = 3 to T = 8. We fitted one-dimensional luminosity profiles with physically motivated functions-the solutions of two stellar and one gaseous isothermal coupled disks in equilibrium-which are likely to yield more accurate results than other functions used in previous studies. The images used for the fits come from the Spitzer Survey of Stellar Structure in Galaxies (S(4)G). We found that thick disks are on average more massive than previously reported, mostly due to the selected fitting function. Typically, the thin and thick disks have similar masses. We also found that thick disks do not flare significantly within the observed range in galactocentric radii and that the ratio of thick-to-thin disk scale heights is higher for galaxies of earlier types. Our results tend to favor an in situ origin for most of the stars in the thick disk. In addition, the thick disk may contain a significant amount of stars coming from satellites accreted after the initial buildup of the galaxy and an extra fraction of stars coming from the secular heating of the thin disk by its own overdensities. Assigning thick disk light to the thin disk component may lead to an underestimate of the overall stellar mass in galaxies because of different mass-to-light ratios in the two disk components. On the basis of our new results, we estimate that disk stellar masses are between 10% and 50% higher than previously thought and we suggest that thick disks are a reservoir of 'local missing baryons.'</P>
Kim, Taehyun,Sheth, Kartik,Hinz, Joannah L.,Lee, Myung Gyoon,Zaritsky, Dennis,Gadotti, Dimitri A.,Knapen, Johan H.,Schinnerer, Eva,Ho, Luis C.,Laurikainen, Eija,Salo, Heikki,Athanassoula, E.,Bosma, Al IOP Publishing 2012 The Astrophysical journal Vol.753 No.1
<P>Tidal debris around galaxies can yield important clues on their evolution. We have identified tidal debris in 11 early-type galaxies (T <= 0) from a sample of 65 early types drawn from the Spitzer Survey of Stellar Structure in Galaxies (S(4)G). The tidal debris includes features such as shells, ripples, and tidal tails. A variety of techniques, including two-dimensional decomposition of galactic structures, were used to quantify the residual tidal features. The tidal debris contributes similar to 3%-10% to the total 3.6 mu m luminosity of the host galaxy. Structural parameters of the galaxies were estimated using two-dimensional profile fitting. We investigate the locations of galaxies with tidal debris in the fundamental plane and Kormendy relation. We find that galaxies with tidal debris lie within the scatter of early-type galaxies without tidal features. Assuming that the tidal debris is indicative of recent gravitational interaction or merger, this suggests that these galaxies have either undergone minor merging events so that the overall structural properties of the galaxies are not significantly altered, or they have undergone a major merging events but already have experienced sufficient relaxation and phase mixing so that their structural properties become similar to those of the non-interacting early-type galaxies.</P>
Adams, J,Aggarwal, M M,Ahammed, Z,Amonett, J,Anderson, B D,Anderson, M,Arkhipkin, D,Averichev, G S,Bai, Y,Balewski, J,Barannikova, O,Barnby, L S,Baudot, J,Bekele, S,Belaga, V V,Bellingeri-Laurikainen, Institute of Physics Publishing 2007 Journal of Physics. G, Nuclear and Particle Physic Vol.34 No.3
<P>We present the first study of the energy dependence of <I>p<SUB>t</SUB></I> angular correlations inferred from event-wise mean transverse momentum 〈<I>p<SUB>t</SUB></I>〉 fluctuations in heavy ion collisions. We compare our large-acceptance measurements at CM energies <img SRC='http://ej.iop.org/images/0954-3899/34/3/004/jpg233147ieqn1.gif' ALIGN='MIDDLE' ALT='\sqrt{s_{\rm NN}} = 19.6'/>, 62.4, 130 and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. <I>p<SUB>t</SUB></I> angular correlation structure suggests that the principal source of <I>p<SUB>t</SUB></I> correlations and fluctuations is minijets (minimum-bias parton fragments). We observe a dramatic increase in correlations and fluctuations from SPS to RHIC energies, increasing linearly with <img SRC='http://ej.iop.org/images/0954-3899/34/3/004/jpg233147ieqn2.gif' ALIGN='MIDDLE' ALT='\ln \sqrt{s_{\rm NN}} '/> from the onset of observable jet-related 〈<I>p<SUB>t</SUB></I>〉 fluctuations near 10 GeV.</P>