ترغب بنشر مسار تعليمي؟ اضغط هنا

An infrared study of the double nucleus in NGC3256

289   0   0.0 ( 0 )
 نشر من قبل Paulina Lira
 تاريخ النشر 2007
  مجال البحث فيزياء
والبحث باللغة English
 تأليف P.Lira




اسأل ChatGPT حول البحث

We present new resolved near and mid-IR imaging and N-band spectroscopy of the two nuclei in the merger system NGCA3256, the most IR luminous galaxy in the nearby universe. The results from the SED fit to the data are consistent with previous estimates of the amount of obscuration towards the nuclei and the nuclear star formation rates. However, we also find substantial differences in the infrared emission from the two nuclei which cannot be explained by obscuration alone. We conclude that the northern nucleus requires an additional component of warm dust in order to explain its properties. This suggests that local starforming conditions can vary significantly within the environment of a single system.

قيم البحث

اقرأ أيضاً

67 - Bjorn Emonts 2014
The nuclei of merging galaxies are often deeply buried in dense layers of gas and dust. In these regions, gas outflows driven by starburst and AGN activity are believed to play a crucial role in the evolution of these galaxies. However, to fully unde rstand this process it is essential to resolve the morphology and kinematics of such outflows. Using near-IR integral-field spectroscopy obtained with VLT/SINFONI, we detect a kpc-scale structure of high-velocity molecular hydrogen (H2) gas associated with the deeply buried secondary nucleus of the IR-luminous merger NGC3256. We show that this structure is likely the hot component of a molecular outflow, which is detected also in the cold molecular gas by Sakamoto et al. This outflow, with a molecular gas mass of M(H2)~2x10^7 Msun, is among the first to be spatially resolved in both the hot H2 gas with VLT/SINFONI and the cold CO-emitting gas with ALMA. The hot and cold components share a similar morphology and kinematics, with a hot-to-cold molecular gas mass ratio of ~6x10^-5. The high (~100 pc) resolution at which we map the geometry and velocity structure of the hot outflow reveals a biconical morphology with opening angle ~40 deg and gas spread across a FWZI~1200 km/s. Because this collimated outflow is oriented close to the plane of the sky, the molecular gas may reach maximum intrinsic outflow velocities of ~1800 km/s, with an average mass outflow rate of at least ~20 Msun/yr. By modeling the line-ratios of various near-IR H2 transitions, we show that the H2 gas in the outflow is heated through shocks or X-rays to a temperature of ~1900K. The energy needed to drive the outflow is likely provided by a hidden Compton-thick AGN or by the nuclear starburst. We show that the global kinematics of the molecular outflow in NGC3256 mimic those of CO-outflows that have been observed at low spatial resolution in starburst- and active galaxies.
We investigate signs of Active Galactic Nucleus (AGN) in the luminous infrared galaxy NGC 3256 at both infrared and X-ray wavelengths. NGC 3256 has double, the Northern and Southern, nuclei (hereafter, N and S nuclei, respectively). We show that the Spitzer IRAC colors extracted at the S nucleus are AGN-like, and the Spitzer IRS spectrum is bluer at <6um than at the N nucleus. We built for the S nucleus an AGN-starburst composite model with a heavily absorbed AGN to successfully reproduce not only the IRAC and IRS specrophotometries at ~3arcsec but also the very deep silicate 9.7um absorption observed at 0.36 scale by Diaz-Santos et al. We found a 2.2um compact source at the S nucleus in a HST NICMOS image and identified its unresolved core (at 0.26 resolution) with the compact core in previous mid-infrared observations at comparable resolution. The flux of the 2.2umm core is consistent with our AGN spectral energy distribution model. We also analyzed a deeper than ever Chandra X-ray spectrum of the unresolved (at 0.5 resolution) source at the S nucleus. We found that a dual-component power-law model (for primary and scattered ones) fits an apparently very hard spectrum with a moderately large absorption on the primary component. Together with a limit on equivalent width of a fluorescent Fe-K emission line at 6.4 keV, the X-ray spectrum is consistent with a typical Compton-thin Seyfert 2. We therefore suggest that the S nucleus hosts a heavily absorbed low-luminosity AGN.
NGC 4490/85 (UGC 7651/48) or Arp 269 is well known for being one of the closest interacting/merging galactic systems. NGC 4490 has a high star formation rate (SFR) and is surrounded by an enormous HI feature stretching about 60 kpc north and south of the optically visible galaxies. Both the driver for the high SFR in NGC 4490 and the formation mechanism of the HI structure are puzzling aspects of this system. We have used mid-infrared Spitzer data to show that NGC 4490 has a double nucleus morphology. One nucleus is visible in the optical, while the other is only visible at infrared and radio wavelengths. We find the optical nucleus and the potential infrared visible nucleus have similar sizes, masses, and luminosities. Both are comparable in mass and luminosity to other nuclei found in interacting galaxy pairs and much more massive and luminous compared with typical non-nuclear star-forming complexes. We examine possible origin scenarios for the infrared feature, and conclude that it is likely that NGC 4490 is itself a merger remnant, which is now interacting with NGC 4485. This earlier encounter provides both a possible driver for extended star formation in NGC 4490, and multiple pathways for the formation of the extended HI plume.
119 - Piero Ranalli 2012
Charge-exchange (CE) emission produces features which are detectable with the current X-ray instrumentation in the brightest near galaxies. We describe these aspects in the observed X-ray spectra of the star forming galaxies M82 and NGC 3256, from th e Suzaku and XMM-Newton telescopes. Emission from both ions (O, C) and neutrals (Mg, Si) is recognised. We also describe how microcalorimeter instrumentation on future missions will improve CE observations.
We present a detailed study of chemical freeze-out in nucleus-nucleus collisions at beam energies of 11.6, 30, 40, 80 and 158A GeV. By analyzing hadronic multiplicities within the statistical hadronization approach, we have studied the strangeness pr oduction as a function of centre of mass energy and of the parameters of the source. We have tested and compared differe
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا