اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدAn Atlas of H-alpha and R Images and Radial Profiles of 29 Bright Isolated Spiral Galaxies
86
0
0.0
(
0
)
تأليف
R. A. Koopmann
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Narrow-band H-alpha+[NII] and broadband R images and surface photometry are presented for a sample of 29 bright (M_B < -18) isolated S0-Scd galaxies within a distance of 48 Mpc. These galaxies are among the most isolated nearby spiral galaxies of their Hubble classifications as determined from the Nearby Galaxies Catalog (Tully 1987a).
قيم البحث
اقرأ أيضاً
In this second paper on the investigation of extraplanar diffuse ionized gas in nearby edge-on spiral galaxies we present the actual results of the individual galaxies of our H-alpha imaging survey. A grand total of 74 galaxies have been studied, inc
luding the 9 galaxies of a recently studied sub-sample (Rossa & Dettmar 2000). 40.5% of all studied galaxies reveal extraplanar diffuse ionized gas, whereas in 59.5% of the survey galaxies no extraplanar diffuse ionized gas could be detected. The average distances of this extended emission above the galactic midplane range from 1-2 kpc, while individual filaments in a few galaxies reach distances of up to |z| ~ 6 kpc. In several cases a pervasive layer of ionized gas was detected, similar to the Reynolds layer in our Milky Way, while other galaxies reveal only extended emission locally. The morphology of the diffuse ionized gas is discussed for each galaxy and is compared with observations of other important ISM constituents in the context of the disk-halo connection, in those cases where published results were available. Furthermore, we present the distribution of extraplanar dust in these galaxies, based on an analysis of the unsharp-masked R-band images. The results are compared with the distribution of the diffuse ionized gas.
We present the mass models of 31 spiral and irregular nearby galaxies obtained using hybrid rotation curves (RCs) combining high resolution GHASP Fabry-Perot H$alpha$ RCs and extended WHISP HI ones together with 3.4 $mu$m WISE photometry. The aim is
to compare the dark matter (DM) halo properties within the optical radius using only H$alpha$ RCs with the effect of including and excluding the mass contribution of the neutral gas component, and when using HI or hybrid RCs. Pseudo-isothermal (ISO) core and Navarro-Frenk-White (NFW) cuspy DM halo profiles are used with various fiducial fitting procedures. Mass models using H$alpha$ RCs including or excluding the HI gas component provide compatible disc M/L. The correlations between DM halo and baryon parameters do not strongly depend on the RC. Clearly, the differences between the fitting procedures are larger than between the different datasets. Hybrid and HI RCs lead to higher M/L values for both ISO and NFW best fit models but lower central densities for ISO halos and higher concentration for NFW halos than when using H$alpha$ RCs only. The agreement with the mass model parameters deduced using hybrid RCs, considered as a reference, is better for HI than for H$alpha$ RCs. ISO density profiles better fit the RCs than the NFW ones, especially when using H$alpha$ or hybrid RCs. Halo masses at the optical radius determined using the various datasets are compatible even if they tend to be overestimated with H$alpha$ RCs. Hybrid RCs are thus ideal to study the mass distribution within the optical radius.
We use the SDSS/DR8 galaxy sample to study the radial distribution of satellite galaxies around isolated primaries, comparing to semi-analytic models of galaxy formation based on the Millennium and Millennium-II simulations. SDSS satellites behave di
fferently around high- and low-mass primaries: those orbiting objects with $M_*>10^{11}M_odot$ are mostly red and are less concentrated towards their host than the inferred dark matter halo, an effect that is very pronounced for the few blue satellites. On the other hand, less massive primaries have steeper satellite profiles that agree quite well with the expected dark matter distribution and are dominated by blue satellites, even in the inner regions where strong environmental effects are expected. In fact, such effects appear to be strong only for primaries with $M_* > 10^{11}M_odot$. This behaviour is not reproduced by current semi-analytic simulations, where satellite profiles always parallel those of the dark matter and satellite populations are predominantly red for primaries of all masses. The disagreement with SDSS suggests that environmental effects are too efficient in the models. Modifying the treatment of environmental and star formation processes can substantially increase the fraction of blue satellites, but their radial distribution remains significantly shallower than observed. It seems that most satellites of low-mass primaries can continue to form stars even after orbiting within their joint halo for 5 Gyr or more.
We present the results of low dispersion optical spectroscopy of 186 H II regions spanning a range of radius in 13 spiral galaxies. Abundances for several elements (oxygen, nitrogen, neon, sulfur, and argon) were determined for 185 of the H II region
s. As expected, low metallicities were found for the outlying H II regions of these spiral galaxies. Radial abundance gradients were derived for the 11 primary galaxies; similar to results for other spiral galaxies, the derived abundance gradients are typically -0.04 to -0.07 dex/kpc.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
