Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userTotal Opacity of Local Group Galaxies and Large Scale Structure behind the Galactic Bulge
54
0
0.0
(
0
)
Authors
Rosa A. Gonzalez
Ask ChatGPT about the research
No Arabic abstract
Recently, we have developed and calibrated the Synthetic Field Method to derive total extinction through disk galaxies. The method is based on the number counts and colors of distant background field galaxies that can be seen through the foreground object. Here, we investigate how large (10-m) and very large (20 to 30-m), diffraction-limited, optical and infrared telescopes in space would improve the detection of background galaxies behind Local Group objects, including the Galactic bulge. We find that, besides and perhaps more important than telescope size, a well-behaved, well-characterized PSF would facilitate in general the detection of faint objects in crowded fields, and greatly benefit several other important research areas, like the search for extrasolar planets, the study of quasar hosts and, most relevant for this meeting, the surveying of nearby large scale structure in the Zone of Avoidance, in particular behind the Galactic bulge.
rate research
Read More
We study the dependence of the properties of group galaxies on the surrounding large-scale environment, using SDSS-DR7 data. Galaxies are ranked according to their luminosity within each group and classified morphologically by the Sersic index. We have considered samples of the host groups in superstructures of galaxies, and elsewhere. We find a significant dependence of the properties of late-type brightest group galaxies on the large-scale environment: they show statistically significant higher luminosities and stellar masses, redder u-r colours, lower star formation activity and longer star-formation time-scale when embedded in superstructures. By contrast, the properties of the early-type brightest group galaxies are remarkably similar regardless of the group global environment. The other group member galaxies exhibit only the local influence of the group they inhabit. Our analysis comprises tests against the dependence on the host group luminosity and we argue that group brightest member properties are not only determined by the host halo, but also by the large-scale structure which can influence the accretion process onto their late-type brightest galaxies.
Suzaku and Chandra X-ray observations detected a new cluster of galaxies, Suzaku J1759-3450, at a redshift z=0.13. It is located behind the Milky Way, and the high Galactic dust extinction renders it nearly invisible at optical wavelengths. We attempt here to confirm the galaxy cluster with near-infrared imaging observations, and to characterize its central member galaxies. Images from the VVV survey were used to detect candidate member galaxies of Suzaku J1759-3450 within the central region of the cluster, up to 350 kpc from the X-ray peak emission. Color-magnitude and color-color diagrams and morphology criteria allowed us to select the galaxies among the numerous foreground sources. Fifteen candidate cluster members were found very close to a modeled red-sequence at the redshift of the cluster. Five members are extremely bright, and one is possibly a cD galaxy. The asymmetry in the spatial distribution of the galaxies respect to the X-ray peak emission is an indicator of that this cluster is still suffering a virialization process. Our investigation of Suzaku J1759-3450 demonstrates the potential of the VVV Survey to study the hidden population of galaxies in the Zone of Avoidance.
We present a three-dimensional study of the local (<100 h^-1} kpc) and the large scale (<1 h^{-1} Mpc) environment of the two main types of Seyfert AGN galaxies. For this purpose we use 48 Sy1 galaxies (with redshifts in the range 0.007<z<0.036) and 56 Sy2 galaxies (with 0.004<z<0.020), located at high galactic latitudes, as well as two control samples of non-active galaxies having the same morphological, redshift, and diameter size distributions as the corresponding Seyfert samples. Using the Center for Astrophysics (CfA2) and Southern Sky Redshift Survey (SSRS) galaxy catalogues (m_B~15.5) and our own spectroscopic observations (m_B~18.5), we find that within a projected distance of 100 h^-1 kpc and a radial velocity separation of dv<600 km/sec around each of our AGNs, the fraction of Seyfert 2 galaxies with a close neighbor is significantly higher than that of their control (especially within 75 h^{-1} kpc) and Seyfert 1 galaxy samples, confirming a previous two-dimensional analysis of Dultzin-Hacyan et al. We also find that the large-scale environment around the two types of Seyfert galaxies does not vary with respect to their control sample galaxies. However, in the Seyfert 2 and control galaxy samples do differ significantly when compared to the corresponding Seyfert 1 samples. Since the main difference between these samples is their morphological type distribution, we argue that the large-scale environmental difference cannot be attributed to differences in nuclear activity but rather to their different type of host galaxies.
Recent observations of the fields surrounding a few Milky-Way-like galaxies in the local Universe have become deep enough to enable investigations of the predictions of the standard LCDM cosmological model down to small scales outside the Local Group. Motivated by an observed correlation between the number of dwarf satellites (N_sat) and the bulge-to-total baryonic mass ratios (B/T) of the three main galaxies in the Local Group, i.e. the Milky Way, Andromeda, and Triangulum (M33), we use published data of three well-studied galaxies outside the Local Group, namely M81, Centaurus A, and M101, and their confirmed satellites, and we find a strong and significant correlation between N_sat and B/T. This presents itself in contradiction with the hitherto published results from cosmological simulations reporting an absence of a correlation between N_sat and B/T in the LCDM model. We conclude that, based on the current data, the N_sat vs. B/T correlation is no longer a property confined to only the Local Group.
Based on the Sloan Digital Sky Survey DR6 (SDSS) and Millennium Simulation (MS) we investigate the alignment between galaxies and large-scale structure. For this purpose we develop two new statistical tools, namely the alignment correlation function and the cos(2theta)-statistic. The former is a two-dimensional extension of the traditional two-point correlation function and the latter is related to the ellipticity correlation function used for cosmic shear measurements. Both are based on the cross correlation between a sample of galaxies with orientations and a reference sample which represents the large-scale structure. Applied to the SDSS galaxy catalog the alignment correlation function reveals an overabundance of reference galaxies along the major axes of red, luminous (L > L*) galaxies out to projected separations of 60 Mpc/h. No alignment signal is detected for blue galaxies. The cos(2theta)-statistic yields very similar results. Starting from a MS semi-analytic galaxy catalog we assign an orientation to each red, luminous and central galaxy, based on the central region of the host halo. Alternatively, we use the orientation of the host halo itself. We find a mean projected misalignment between a halo and its central region of ~25 deg. Agreement with the SDSS results is good if the central orientations are used. Using the halo orientations overestimates the observed alignment by more than a factor of 2. The large volume of the MS allows to generate two-dimensional maps of the alignment correlation function which show the reference galaxy distribution to be flattened parallel to the orientations of red luminous galaxies with axis ratios of ~0.5 and ~0.75 for halo and central orientations,respectively. These ratios are almost independent of scale out to 60 Mpc/h.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
