118439902
Jets and environment of microquasars
Two relativistic X-ray jets have been detected with the Chandra X-ray observatory from the black hole X-ray transient XTE J1550-564. We report a full analysis of the evolution of the two jets with a gamma-ray burst external shock model. A plausible scenario suggests a cavity outside the central source and the jets first travelled with constant velocity and then are slowed down by the interactions between the jets and the interstellar medium (ISM). The best fitted radius of the cavity is $\sim$0.36 pc on the eastern side and $\sim$0.46 pc on the western side, and the densities also show asymmetry, of $\sim$0.015 cm$^{-3}$ on the east to $\sim$0.21 cm$^{-3}$ on the west. A large scale low density region is also found in another microquasar system, H 1743-322. These results are consistent with previous suggestions that the environment of microquasars should be rather vacuous, compared to the normal Galactic environment. A generic scenario for microquasar jets is proposed, classifying the observed jets into three main categories, with different jet morphologies (and sizes) corresponding to different scales of vacuous environments surrounding them.
16218923
Evolution of relativistic jets from XTE J1550‐564 and the environment of microquasars
Two relativistic X‐ray jets have been detected with the Chandra X‐ray observatory in the black hole X‐ray transient XTE J1550‐564. We report a full analysis of the evolution of the two jets with a gamma‐ray burst external shock model. A plausible scenario suggests a cavity outside the central source and the jets first travelled with constant velocity and then are slowed down by the interactions between the jets and the interstellar medium (ISM). The best fitted radius of the cavity is ∼0.36 pc on the eastern side and ∼0.46 pc on the western side, and the densities also show asymmetry, of ∼0.015 cm−3 on the east to ∼0.21 cm−3 on the west. Large scale low density region is also found in another microquasar system, H 1743‐322. These results are consistent with previous suggestions that the environment of microquasars should be rather vacuous, compared to the normal Galactic environment. A generic scenario for microquasar jets is proposed, classifying the observed jets into three main categories, with differe...
14496803
LARGE-SCALE CAVITIES SURROUNDING MICROQUASARS INFERRED FROM EVOLUTION OF THEIR RELATIVISTIC JETS
The black hole (BH) X-ray transient XTE J1550-564 has undergone a strong outburst in 1998 and two relativistic X-ray jets have been detected years later with the Chandra X-ray observatory; the eastern jet was found previously to have decelerated after its first detection. Here, we report a full analysis of the evolution of the western jet; significant deceleration is also detected in the western side. Our analysis indicates that there is a cavity outside the central source and the jets first traveled with constant velocity and then were slowed down by the interactions between the jets and the interstellar medium. The best-fitted radius of the cavity is similar to 0.31 pc on the eastern side and similar to 0.44 pc on the western side, and the densities also show asymmetry, of similar to 0.034 cm(-3) on the east to similar to 0.12 cm(-3) on the west. The best-fitted magnetic fields on both sides are similar to 0.5 mG. Similar analysis is also applied to another microquasar system, H 1743-322, and a large-scale low-density region is also found. Based on these results and the comparison with other microquasar systems, we suggest a generic scenario for microquasar jets, classifying the observed jets into three main categories, with different jet morphologies (and sizes) corresponding to different scales of vacuous environments surrounding them. We also suggest that either continuous jets or accretion disk winds, or both may be responsible for creating these cavities. Therefore X-ray jets from microquasars provide us with a promising method of probing the environment of accreting BHs.
197484385
Can Relativistic MOND Theory Resolve Both the Dark Matter and Dark Energy Paradigms
7268824
Precision Measurements of the Cluster Red Sequence Using an Error-Corrected Gaussian Mixture Model
The red sequence is an important feature of galaxy clusters and plays a crucial role in optical cluster detection. Measurement of the slope and scatter of the red sequence are affected both by selection of red sequence galaxies and measurement errors. In this paper, we describe a new error-corrected Gaussian Mixture Model for red sequence galaxy identification. Using this technique, we can remove the effects of measurement error and extract unbiased information about the intrinsic properties of the red sequence. We use this method to select red sequence galaxies in each of the 13,823 clusters in the maxBCG catalog, and measure the red sequence ridgeline location and scatter of each. These measurements provide precise constraints on the variation of the average red galaxy populations in the observed frame with redshift. We find that the scatter of the red sequence ridgeline increases mildly with redshift, and that the slope decreases with redshift. We also observe that the slope does not strongly depend on cluster richness. Using similar methods, we show that this behavior is mirrored in a spectroscopic sample of field galaxies, further emphasizing that ridgeline properties are independent of environment. These precise measurements serve as an important observational check on simulations and mock galaxy catalogs. The observed trends in the slope and scatter of the red sequence ridgeline with redshift are clues to possible intrinsic evolution of the cluster red sequence itself. Most importantly, the methods presented in this work lay the groundwork for further improvements in optically based cluster cosmology.
118378015
ROBUST OPTICAL RICHNESS ESTIMATION WITH REDUCED SCATTER
Reducing the scatter between cluster mass and optical richness is a key goal for cluster cosmology from photometric catalogs. We consider various modifications to the red-sequence-matched filter richness estimator of Rozo et al. implemented on the maxBCG cluster catalog and evaluate the impact of these changes on the scatter in X-ray luminosity (L{sub X} ) at fixed richness, using L{sub X} from the ROSAT All-Sky Catalog as the best mass proxy available for the large area required. Most significantly, we find that deeper luminosity cuts can reduce the recovered scatter, finding that {sigma}{sub ln{sub L{sub x|{lambda}}}}=0.63{+-}0.02 for clusters with M{sub 500c} {approx}> 1.6 Multiplication-Sign 10{sup 14} h{sup -1}{sub 70} M{sub Sun }. The corresponding scatter in mass at fixed richness is {sigma}{sub lnM|{lambda}} Almost-Equal-To 0.2-0.3 depending on the richness, comparable to that for total X-ray luminosity. We find that including blue galaxies in the richness estimate increases the scatter, as does weighting galaxies by their optical luminosity. We further demonstrate that our richness estimator is very robust. Specifically, the filter employed when estimating richness can be calibrated directly from the data, without requiring a priori calibrations of the red sequence. We also demonstrate that the recovered richness is robust tomore » up to 50% uncertainties in the galaxy background, as well as to the choice of photometric filter employed, so long as the filters span the 4000 A break of red-sequence galaxies. Consequently, our richness estimator can be used to compare richness estimates of different clusters, even if they do not share the same photometric data. Appendix A includes 'easy-bake' instructions for implementing our optimal richness estimator, and we are releasing an implementation of the code that works with Sloan Digital Sky Survey data, as well as an augmented maxBCG catalog with the {lambda} richness measured for each cluster.« less
120057201
Testing the Dark Energy Camera on a telescope simulator
The Dark Energy Camera is a new prime-focus instrument to be delivered to the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO) in 2011. Construction is in-progress at this time at Fermilab. In order to verify that the camera meets technical specifications for the Dark Energy Survey and to reduce the time required to commission the instrument while it is on the telescope, we are constructing a "Telescope Simulator" and performing full system testing prior to shipping to CTIO. This presentation will describe the Telescope Simulator and how we use it to verify some of the technical specifications.