اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe Star Formation History of the Hubble Sequence: Spatially Resolved Colour Distributions of Intermediate Redshift Galaxies in the Hubble Deep Field
71
0
0.0
(
0
)
تأليف
R. G. Abraham
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We analyse the spatially resolved colours of distant galaxies of known redshift in the Hubble Deep Field, using a new technique based on matching resolved four-band internal colour data to the predictions of evolutionary synthesis models. We quantify the relative age, dispersion in age, ongoing star-formation rate, star-formation history, and dust content of these galaxies. To demonstrate the potential of the method, we study the near-complete sample of 32 I<21.9 mag galaxies with <z> ~ 0.5 studied by Bouwens et al (1997). The dispersion of the internal colours of a sample of 0.4<z<1 early-type field galaxies in the HDF indicates that ~40% [4/11] show evidence of star formation which must have occurred within the past third of their ages at the epoch of observation. For a sample of well-defined spirals, we similarly exploit the dispersion in colour to analyse the relative histories of bulge and disc stars, in order to resolve the current controversy regarding the ages of galactic bulges. Dust and metallicity gradients are ruled out as major contributors to the colour dispersions we observe in these systems. The median ages of bulge stars are found to be signicantly older than those in galactic discs, and exhibit markedly different star-formation histories. This result is inconsistent with a secular growth of bulges from disc instabilities, but consistent with gradual disc formation by accretion of gas onto bulges, as predicted by hierarchical theories. We extend our technique in order to discuss the star formation history of the entire Bouwens et al sample in the context of earlier studies concerned with global star formation histories.
قيم البحث
اقرأ أيضاً
This paper presents the star formation history in the NICMOS Northern Deep HDF. It uses the techniques of photometric redshifts and extinctions to correct for extinction of the ultra-violet flux. It presents a new method for correcting for surface br
ightness diming. It also predicts the 850 micron fluxes of the objects for comparison with SCUBA measurements
We use the NICMOS Treasury and ACS HUDF images to measure the extinction corrected star formation history for 4681 galaxies in the region common to both images utilizing the star formation rate distribution function and other techniques similar to th
ose employed with the NICMOS and WFPC2 images in the HDFN. Unlike the HDFN the NICMOS region of the HUDF appears to lack highly luminous and high star formation rate galaxies at redshifts beyond 3. The HUDF provides a region that is completely uncorrelated to the HDFN and therefore provides and independent measure of the star formation history of the universe. The combined HUDF and HDFN star formation rates show an average star formation rate of 0.2 solar masses per yer per cubic megaparsec. The average SFR of the combined fields at z = 1-3 is 0.29 solar masses per year per cubic megaparsec while the average at z = 4-6 is 1.2 solar masses per year per cubic megaparsec. The SFRs at all redshifts are within 3 sigma of the average over all redshifts.
We analyze the photometric information contained in individual pixels of galaxies in the Hubble Deep Field North (HDFN) using a new technique, _pixel-z_, that combines predictions of evolutionary synthesis models with photometric redshift template fi
tting. Each spectral energy distribution template is a result of modeling of the detailed physical processes affecting gas properties and star formation efficiency. The criteria chosen to generate the SED templates is that of sampling a wide range of physical characteristics such as age, star formation rate, obscuration and metallicity. A key feature of our method is the sophisticated use of error analysis to generate error maps that define the reliability of the template fitting on pixel scales and allow for the separation of the interplay among dust, metallicity and star formation histories. This technique offers a number of advantages over traditional integrated color studies. As a first application, we derive the star formation and metallicity histories of galaxies in the HDFN. Our results show that the comoving density of star formation rate, determined from the UV luminosity density of sources in the HDFN, increases monotonically with redshift out to at least redshift of 5. This behavior can plausibly be explained by a smooth increase of the UV luminosity density with redshift coupled with an increase in the number of star forming regions as a function of redshift. We also find that the information contained in individual pixels in a galaxy can be linked to its morphological history. Finally, we derive the metal enrichment rate history of the universe and find it in good agreement with predictions based on the evolving HI content of Lyman-alpha QSO absorption line systems.
We combine the latest observations of disk galaxy photometry and rotation curves at moderate redshift from the FORS Deep Field (FDF) with simple models of chemical enrichment. Our method describes the buildup of the stellar component through infall o
f gas and allows for gas and metal outflows. In this framework, we keep a minimum number of constraints and we search a large volume of parameter space, looking for the models which best reproduce the photometric observations in the observed redshift range (0.5<z<1). We find the star formation efficiency to correlate well with vMAX so that massive disks are more efficient in the formation of stars and have a smaller spread in stellar ages. This trend presents a break at around vMAX 140km/s. Galaxies on either side of this threshold have significantly different age distributions. This break has been already suggested by several authors in connection with the contribution from either gravitational instabilities or supernova-driven turbulence to star formation. No clear trend is seen between galaxy mass and infall timescale or gas outflows. The model presented in this paper suggests massive disks have formation histories resembling those of early-type galaxies, with highly efficient and short-lived bursts, in contrast with low-mass disks, which have a more extended star formation history. One option to explain the observed shallow slope of the Tully-Fisher relation at intermediate redshift could be small episodes of star formation in low-mass disks.
The aim of this paper is to characterize the radial structure of the star formation rate (SFR) in galaxies in the nearby Universe as represented by the CALIFA survey. The sample under study contains 416 galaxies observed with IFS, covering a wide ran
ge of Hubble types and stellar masses. Spectral synthesis techniques are applied to obtain radial profiles of the intensity of the star formation rate in the recent past, and the local sSFR. To emphasize the behavior of these properties for galaxies that are on and off the main sequence of star formation (MSSF) we stack the individual radial profiles in bins of galaxy morphology and stellar masses. Our main results are: a) The intensity of SFR shows declining profiles that exhibit very little differences between spirals. The dispersion between the profiles is significantly smaller in late type spirals. This confirms that the MSSF is a sequence of galaxies with nearly constant intensity of SFR b) sSFR values scale with Hubble type and increase radially outwards, with a steeper slope in the inner 1 HLR. This behavior suggests that galaxies are quenched inside-out, and that this process is faster in the central, bulge-dominated part than in the disks. c) As a whole, and at all radii, E and S0 are off the MSSF. d) Applying the volume-corrections for the CALIFA sample, we obtain a density of star formation in the local Universe of 0.0105 Msun/yr/Mpc^{-3}. Most of the star formation is occurring in the disks of spirals. e) The volume averaged birthrate parameter, b=0.39, suggests that the present day Universe is forming stars at 1/3 of its past average rate. E, S0, and the bulge of early type spirals contribute little to the recent SFR of the Universe, which is dominated by the disks of later spirals. f) There is a tight relation between the intensity of the SFR and stellar mass, defining a local MSSF relation with a logarithmic slope of 0.8.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
