اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدGas Dynamics and Star Formation in the Galaxy Pair NGC1512/1510
211
0
0.0
(
0
)
تأليف
Baerbel S. Koribalski
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
(abridged) Here we present HI line and 20-cm radio continuum data of the nearby galaxy pair NGC1512/1510 as obtained with the Australia Telescope Compact Array. These are complemented by GALEX UV-, SINGG Halpha- and Spitzer mid-infrared images, allowing us to compare the distribution and kinematics of the neutral atomic gas with the locations and ages of the stellar clusters within the system. For the barred, double-ring galaxy NGC1512 we find a very large HI disk, about 4x its optical diameter, with two pronounced spiral/tidal arms. Both its gas distribution and the distribution of the star-forming regions are affected by gravitational interaction with the neighbouring blue compact dwarf galaxy NGC1510. The two most distant HI clumps, at radii of about 80 kpc, show signs of star formation and are likely tidal dwarf galaxies. Star formation in the outer disk of NGC1512 is revealed by deep optical- and two-color ultraviolet images. Using the latter we determine the properties of about 200 stellar clusters and explore their correlation with dense HI clumps in the even larger 2XHI disk. The multi-wavelength analysis of the NGC1512/1510 system, which is probably in the first stages of a minor merger having started about 400 Myr ago, links stellar and gaseous galaxy properties on scales from one to 100 kpc.
قيم البحث
اقرأ أيضاً
This lecture reviews the fundamental physical processes involved in star formation in galaxy interactions and mergers. Interactions and mergers often drive intense starbursts, but the link between interstellar gas physics, large scale interactions, a
nd active star formation is complex and not fully understood yet. Two processes can drive starbursts: radial inflows of gas can fuel nuclear starbursts, triggered gas turbulence and fragmentation can drive more extended starbursts in massive star clusters with high fractions of dense gas. Both modes are certainly required to account for the observed properties of starbursting mergers. A particular consequence is that star formation scaling laws are not universal, but vary from quiescent disks to starbursting mergers. High-resolution hydrodynamic simulations are used to illustrate the lectures.
We investigate the relationship between star formation (SF) and substructure in a sample of 107 nearby galaxy clusters using data from the Sloan Digital Sky Survey (SDSS). Several past studies of individual galaxy clusters have suggested that cluster
mergers enhance cluster SF, while others find no such relationship. The SF fraction in multi-component clusters (0.228 +/- 0.007) is higher than that in single-component clusters (0.175 +/- 0.016) for galaxies with M^0.1_r < -20.5. In both single- and multi-component clusters, the fraction of star-forming galaxies increases with clustercentric distance and decreases with local galaxy number density, and multi-component clusters show a higher SF fraction than single-component clusters at almost all clustercentric distances and local densities. Comparing the SF fraction in individual clusters to several statistical measures of substructure, we find weak, but in most cases significant at greater than 2 sigma, correlations between substructure and SF fraction. These results could indicate that cluster mergers may cause weak but significant SF enhancement in clusters, or unrelaxed clusters exhibit slightly stronger SF due to their less evolved states relative to relaxed clusters.
We study dwarf galaxy formation at high redshift ($zge5$) using a suite of high- resolution, cosmological hydrodynamic simulations and a semi-analytic model (SAM). We focus on gas accretion, cooling and star formation in this work by isolating the re
levant process from reionization and supernova feedback, which will be further discussed in a companion paper. We apply the SAM to halo merger trees constructed from a collisionless N-body simulation sharing identical initial conditions to the hydrodynamic suite, and calibrate the free parameters against the stellar mass function predicted by the hydrodynamic simulations at z = 5. By making comparisons of the star formation history and gas components calculated by the two modelling techniques, we find that semi-analytic prescriptions that are commonly adopted in the literature of low-redshift galaxy formation do not accurately represent dwarf galaxy properties in the hydrodynamic simulation at earlier times. We propose 3 modifications to SAMs that will provide more accurate high-redshift simulations. These include 1) the halo mass and baryon fraction which are overestimated by collisionless N-body simulations; 2) the star formation efficiency which follows a different cosmic evolutionary path from the hydrodynamic simulation; and 3) the cooling rate which is not well defined for dwarf galaxies at high redshift. Accurate semi-analytic modelling of dwarf galaxy formation informed by detailed hydrodynamical modelling will facilitate reliable semi-analytic predictions over the large volumes needed for the study of reionization.
High resolution, multi-wavelength maps of a sizeable set of nearby galaxies have made it possible to study how the surface densities of HI, H2 and star formation rate (Sigma_HI, Sigma_H2, Sigma_SFR) relate on scales of a few hundred parsecs. At these
scales, individual galaxy disks are comfortably resolved, making it possible to assess gas-SFR relations with respect to environment within galaxies. Sigma_H2, traced by CO intensity, shows a strong correlation with Sigma_SFR and the ratio between these two quantities, the molecular gas depletion time, appears to be constant at about 2Gyr in large spiral galaxies. Within the star-forming disks of galaxies, Sigma_SFR shows almost no correlation with Sigma_HI. In the outer parts of galaxies, however, Sigma_SFR does scale with Sigma_HI, though with large scatter. Combining data from these different environments yields a distribution with multiple regimes in Sigma_gas - Sigma_SFR space. If the underlying assumptions to convert observables to physical quantities are matched, even combined datasets based on different SFR tracers, methodologies and spatial scales occupy a well define locus in Sigma_gas - Sigma_SFR space.
The molecular gas content of local early-type galaxies is constrained and discussed in relation to their evolution. First, as part of the Atlas3D survey, we present the first complete, large (260 objects), volume-limited single-dish survey of CO in n
ormal local early-type galaxies. We find a surprisingly high detection rate of 22%, independent of luminosity and at best weakly dependent on environment. Second, the extent of the molecular gas is constrained with CO synthesis imaging, and a variety of morphologies is revealed. The kinematics of the molecular gas and stars are often misaligned, implying an external gas origin in over a third of the systems, although this behaviour is drastically diffferent between field and cluster environments. Third, many objects appear to be in the process of forming regular kpc-size decoupled disks, and a star formation sequence can be sketched by piecing together multi-wavelength information on the molecular gas, current star formation, and young stars. Last, early-type galaxies do not seem to systematically obey all our usual prejudices regarding star formation, following the standard Schmidt-Kennicutt law but not the far infrared-radio correlation. This may suggest a greater diversity in star formation processes than observed in disk galaxies. Using multiple molecular tracers, we are thus starting to probe the physical conditions of the cold gas in early-types.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
