اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe Star Cluster Population of the Spiral Galaxy NGC3370
128
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Aims.We study the photometric and structural properties of the star cluster system in the late type Sc spiral NGC 3370. Methods. BVI observations from the Advanced Camera for Surveys on board of HST are used to analyse in detail the colours, magnitudes and spatial properties of cluster candidates. The final catalogue of sources used for the study is composed by 277 objects. Results. The colour distributions of cluster candidates appear multi-modal. Although firm age constraints need the use of more age sensitive indicators, the comparison of cluster candidate colours with the colours of Galactic and Magellanic Clouds star clusters, suggests an age difference between the various sub-peaks, with a red old sub-system, a rich population of intermediate age (~1 Gyr), and a blue tail of very young (below ~100 Myr) clusters. The luminosity functions appear normal for this type of galaxy, as for the distribution of cluster effective radii (Reff). Our analysis suggests the presence of a peak in the Reff distribution at ~3.0 pc, with blue (likely young) cluster candidates showing smaller radii respect to red (likely old) objects. Finally, inspecting the properties of candidate globular clusters, we find a colour distribution matching with Galactic Globulars, with a median [Fe/H] -1.5 dex, though a non negligible tail towards lower metallicities is also present.
قيم البحث
اقرأ أيضاً
A rich harvest of RR Lyrae stars has been identified for the first time in B514, a metal-poor ([Fe/H] = 1.95 +/- 0.10 dex) globular cluster of the Andromeda galaxy (M31), based on Hubble Space Telescope Wide Field Planetary Camera 2 and Advanced Came
ra for Surveys time-series observations. We have detected and derived periods for 89 RR Lyrae stars (82 fundamental-mode -RRab- and 7 first-overtone -RRc- pulsators, respectively) among 161 candidate variables identified in the cluster. The average period of the RR Lyrae variables (<Pab> = 0.58 days and <Pc> = 0.35 days, for RRab and RRc pulsators, respectively) and the position in the period-amplitude diagram both suggest that B514 is likely an Oosterhoff type I cluster. This appears to be in disagreement with the general behaviour of the metal-poor globular clusters in the Milky Way, which show instead Oosterhoff type II pulsation properties. The average apparent magnitude of the RR Lyrae stars sets the mean level of the cluster horizontal branch at <V(RR)> = 25.18 +/- 0.02 (sigma=0.16 mag, on 81 stars). By adopting a reddening E(B-V) = 0.07 +/- 0.02 mag, the above metallicity and M_V=0.44 +/- 0.05 mag for the RR Lyrae variables of this metallicity, we derive a distance modulus of mu_0=24.52 +/- 0.08 mag, corresponding to a distance of about 800 +/- 30 kpc, based on a value of M_V that sets mu_0(LMC)=18.52.
(Abridged) Interacting galaxies are well-known for their high star formation rates and rich star cluster populations, but the rapidly changing tidal field can also efficiently destroy clusters. We use numerical simulations of merging disc galaxies to
investigate which mechanism dominates. The simulations include a model for the formation and dynamical disruption of the entire star cluster population. We find that the dynamical heating of clusters by tidal shocks is about an order of magnitude higher in interacting galaxies than in isolated galaxies. This is driven by the increased gas density, and is sufficient to destroy star clusters at a higher rate than new clusters are formed: the total number of clusters in the merger remnant is 2-50% of the amount in the progenitor discs, with low-mass clusters being disrupted preferentially. By adopting observationally motivated selection criteria, we find that the observed surplus of star clusters in nearby merging galaxies is caused by the bias to detect young, massive clusters. We provide a general expression for the survival fraction of clusters, which increases with the gas depletion time-scale. Due to the preferential disruption of low-mass clusters, the mass distribution of the surviving star clusters in a merger remnant develops a peak at a mass of about 10^3 Msun, which evolves to higher masses at a rate of 0.3-0.4 dex per Gyr. The peak mass initially depends weakly on the galactocentric radius, but this correlation disappears as the system ages. We discuss the similarities between the cluster populations of the simulated merger remnants and (young) globular cluster systems. Our results suggest that the combination of cluster formation and destruction should be widespread in the dense star-forming environments at high redshifts, which could provide a natural origin to present-day globular cluster systems.
We present results for X-ray point sources in the Sc galaxy NGC 2276, obtained by analyzing Chandra data. The galaxy is known to be very active in many wavelengths, possibly due to gravitational interaction with the central elliptical of the group, N
GC 2300. However, previous XMM-Newton observations resulted in the detection of only one bright ULX and extended hot gas emission. We present here the X-ray population in NGC 2276 which comprises 17 sources. We found that 6 of them are new ULX sources in this spiral galaxy resolved for the first time by Chandra. We constructed the Luminosity Function that can be interpreted as mainly due of High Mass X-ray binaries, and estimate the Star Formation rate (SFR) to be SFR ~ 5-10 M_sun/yr.
Although there are many more stellar population studies of elliptical and lenticular galaxies, studies of spiral galaxies are catching up, due to higher signal to noise data on one hand, and better analysis methods on the other. Here I start by discu
ssing some modern methods of analyzing integrated spectra of spiral galaxies, and comparing them with traditional methods. I then discuss some recent developments in our understanding of the stellar content of spiral galaxies, and their associated dust content. I discuss star formation histories, radial stellar population gradients, and stellar populations in sigma drops.
We analyzed the massive star population of the Virgo Cluster galaxy NGC 4535 using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in filters F555W and F814W, equivalent to Johnson V and Kron-Cousins I. We performed high precisio
n point spread function fitting photometry of 24353 sources including 3762 candidate blue supergiants, 841 candidate yellow supergiants and 370 candidate red supergiants. We estimated the ratio of blue to red supergiants as a decreasing function of galactocentric radius. Using Modules for Experiments in Stellar Astrophysics isochrones at solar metallicity, we defined the luminosity function and estimated the star formation history of the galaxy over the last 60 Myrs. We conducted a variability search in the V and I filters using three variability indexes: the median absolute deviation, the interquartile range and the inverse von-Neumann ratio. This analysis yielded 120 new variable candidates with absolute magnitudes ranging from M$_{V}$ = $-$4 to $-$11 mag. We used the MESA evolutionary tracks at solar metallicity, to classify the variables based on their absolute magnitude and their position on the color-magnitude diagram. Among the new candidate variable sources are eight candidate variable red supergiants, three candidate variable yellow supergiants and one candidate luminous blue variable, which we suggest for follow-up observations.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
