اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدDust penetrated morphology in the high redshift Universe
145
0
0.0
(
0
)
تأليف
D.L. Block
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Images from the Hubble Deep Field (HDF) North and South show a large percentage of dusty, high redshift galaxies whose appearance falls outside traditional classification systems. The nature of these objects is not yet fully understood. Since the HDF preferentially samples restframe UV light, HDF morphologies are not dust or `mask penetrated. The appearance of high redshift galaxies at near-infrared restframes remains a challenge for the New Millennium. The Next Generation Space Telescope (NGST) could routinely provide us with such images. In this contribution, we quantitatively determine the dust-penetrated structures of high redshift galaxies such as NGC 922 in their near-infrared restframes. We show that such optically peculiar objects may readily be classified using the dust penetrated z ~ 0 templates of Block and Puerari (1999) and Buta and Block (2001).
قيم البحث
اقرأ أيضاً
A simple optical to mid-IR color selection, R-[24] > 14, i.e. f_nu(24) / f_nu(R) > 1000, identifies highly dust obscured galaxies (DOGs) with typical redshifts of z~2 +/- 0.5. Extreme mid-IR luminosities (L_{IR} > 10^{12-14}) suggest that DOGs are po
wered by a combination of AGN and star formation, possibly driven by mergers. In an effort to compare their photometric properties with their rest frame optical morphologies, we obtained high spatial resolution (0.05 -0.1) Keck Adaptive Optics (AO) K-band images of 15 DOGs. The images reveal a wide range of morphologies, including: small exponential disks (8 of 15), small ellipticals (4 of 15), and unresolved sources (2 of 15). One particularly diffuse source could not be classified because of low signal to noise ratio. We find a statistically significant correlation between galaxy concentration and mid-IR luminosity, with the most luminous DOGs exhibiting higher concentration and smaller physical size. DOGs with high concentration also tend to have spectral energy distributions (SEDs) suggestive of AGN activity. Thus central AGN light may be biasing the morphologies of the more luminous DOGs to higher concentration. Conversely, more diffuse DOGs tend to show an SED shape suggestive of star formation. Two of fifteen in the sample show multiple resolved components with separations of ~1 kpc, circumstantial evidence for ongoing mergers.
I present various simulations of an on-going large sub-mm survey, SHADES, showing how constraints can be put on galaxy formation models and cosmology from this survey.
The detection of powerful near-infrared emission in high redshift (z>5) quasars demonstrates that very hot dust is present close to the active nucleus also in the very early universe. A number of high-redshift objects even show significant excess emi
ssion in the rest frame NIR over more local AGN spectral energy distribution (SED) templates. In order to test if this is a result of the very high luminosities and redshifts, we construct mean SEDs from the latest SDSS quasar catalogue in combination with MIR data from the WISE preliminary data release for several redshift and luminosity bins. Comparing these mean SEDs with a large sample of z>5 quasars we could not identify any significant trends of the NIR spectral slope with luminosity or redshift in the regime 2.5 < z < 6 and 10^45 < nuL_nu(1350AA) < 10^47 erg/s. In addition to the NIR regime, our combined Herschel and Spitzer photometry provides full infrared SED coverage of the same sample of z>5 quasars. These observations reveal strong FIR emission (L_FIR > 10^13 L_sun) in seven objects, possibly indicating star-formation rates of several thousand solar masses per year. The FIR excess emission has unusally high temperatures (T ~ 65 K) which is in contrast to the temperature typically expected from studies at lower redshift (T ~ 45 K). These objects are currently being investigated in more detail.
Using self-consistent cosmological simulations of disc galaxy formation, we analyse the 1.4 GHz radio flux from high-redshift progenitors of present-day normal spirals within the context of present-day and planned next-generation observational facili
ties. We demonstrate that while current radio facilities such as the Very Large Array (VLA) are unlikely to trace these progenitors beyond redshifts z<0.2, future facilities such as the Square Kilometer Array (SKA) will readily probe their characteristics to redshifts z<2, and are likely to provide detections beyond z~3. We also demonstrate that the progenitors of present-day cD galaxies can emit in excess of 10 uJy of flux at redshifts z>1, and may be a non-negligible contributor to the micro-Jansky source counts derived from current deep VLA cm-wave surveys.
The Lyman Continuum photon production efficiency ($xi_{rm ion}$) is a critical ingredient for inferring the number of photons available to reionise the intergalactic medium. To estimate the theoretical production efficiency in the high-redshift Unive
rse we couple the BlueTides cosmological hydrodynamical simulation with a range of stellar population synthesis models. We find Lyman Continuum photon production efficiencies of $log_{10}(xi_{rm ion}/{rm erg^{-1}, Hz})approx 25.1-25.5$ depending on the choice of stellar population synthesis model. These results are broadly consistent with recent observational constraints at high-redshift though favour a model incorporating the effects of binary evolution
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
