اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe shape of the initial cluster mass function: what it tells us about the local star formation efficiency
95
0
0.0
(
0
)
تأليف
G. Parmentier
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We explore how the expulsion of gas from star-cluster forming cloud-cores due to supernova explosions affects the shape of the initial cluster mass function, that is, the mass function of star clusters when effects of gas expulsion are over. We demonstrate that if the radii of cluster-forming gas cores are roughly constant over the core mass range, as supported by observations, then more massive cores undergo slower gas expulsion. Therefore, for a given star formation efficiency, more massive cores retain a larger fraction of stars after gas expulsion. The initial cluster mass function may thus differ from the core mass function substantially, with the final shape depending on the star formation efficiency. A mass-independent star formation efficiency of about 20 per cent turns a power-law core mass function into a bell-shaped initial cluster mass function, while mass-independent efficiencies of order 40 per cent preserve the shape of the core mass function.
قيم البحث
اقرأ أيضاً
In contrast to their word- or sentence-level counterparts, character embeddings are still poorly understood. We aim at closing this gap with an in-depth study of English character embeddings. For this, we use resources from research on grapheme-color
synesthesia -- a neuropsychological phenomenon where letters are associated with colors, which give us insight into which characters are similar for synesthetes and how characters are organized in color space. Comparing 10 different character embeddings, we ask: How similar are character embeddings to a synesthetes perception of characters? And how similar are character embeddings extracted from different models? We find that LSTMs agree with humans more than transformers. Comparing across tasks, grapheme-to-phoneme conversion results in the most human-like character embeddings. Finally, ELMo embeddings differ from both humans and other models.
We present the results of our HI survey of six loose groups of galaxies analogous to the Local Group. The survey was conducted using the Parkes telescope and the Australia Telescope Compact Array to produce a census of all the gas-rich galaxies and p
otential analogs to the high-velocity clouds (HVCs) within these groups down to M(HI)<10^7 M(sun) as a test of models of galaxy formation. We present the HI mass function and halo mass function for these analogous groups and compare them with the Local Group and other environments. We also demonstrate that our non-detection of HVC analogs in these groups implies that they must have low HI masses and be clustered tightly around galaxies, including around our own Milky Way, and are not distributed throughout the Local Group.
Using a sample of 229618 narrow emission-line galaxies, we have determined the normal star formation histories (SFHs) for galaxies with different activity types: star forming galaxies (SFGs), transition type objects (TOs), Seyfert 2s (Sy2s) and LINER
s. We find that the variation of the SFH with the activity type is explained by the mass of the galaxies and the importance of their bulge: the LINERs reside in massive early-type galaxies, the Sy2s and TOs are hosted by intermediate mass galaxies with intermediate morphological types, and the SFGs are found in lower mass late-type spirals. Except for the Sy2s, the more massive galaxies formed the bulk of their stars more rapidly than the less massive ones. The Sy2s formed their stars more slowly and show presently an excess in star formation. We have also found that the maximum in star formation rate in the past increases with the virial mass within the aperture (VMA), the VMA increasing from the SFGs to the TOs, to the Sy2s, culminating in the LINERs. This correlation suggests that the bulges and the supermassive black holes at the center of galaxies grow in parallel, in good agreement with the M(BH)-sigma relation.
We discuss the possibility that gravitational focusing, is responsible for the power-law mass function of star clusters $N(log M) propto M^{-1}$. This power law can be produced asymptotically when the mass accretion rate of an object depends upon the
mass of the accreting body as $dot{M} propto M^2$. While Bondi-Hoyle-Littleton accretion formally produces this dependence on mass in a uniform medium, realistic environments are much more complicated. However, numerical simulations in SPH allowing for sink formation yield such an asymptotic power-law mass function. We perform pure N-body simulations to isolate the effects of gravity from those of gas physics and to show that clusters naturally result with the power-law mass distribution. We also consider the physical conditions necessary to produce clusters on appropriate timescales. Our results help support the idea that gravitationally-dominated accretion is the most likely mechanism for producing the cluster mass function.
The stellar initial mass function (IMF) is a fundamental property of star formation, offering key insight into the physics driving the process as well as informing our understanding of stellar populations, their by-products, and their impact on the s
urrounding medium. While the IMF appears to be fairly uniform in the Milky Way disk, it is not yet known how the IMF might behave across a wide range of environments, such as those with extreme gas temperatures and densities, high pressures, and low metallicities. We discuss new opportunities for measuring the IMF in such environments in the coming decade with JWST, WFIRST, and thirty-meter class telescopes. For the first time, we will be able to measure the high-mass slope and peak of the IMF via direct star counts for massive star clusters across the Milky Way and Local Group, providing stringent constraints for star formation theory and laying the groundwork for understanding distant and unresolved stellar systems.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
