ABSTRACT We present the results of a deep imaging survey of the Virgo cluster of galaxies, concentrated around the cores of Virgo subclusters A and B. The goal of this survey was to detect and study ...very low surface brightness features present in Virgo, including discrete tidal features, the faint halos of luminous galaxies, and the diffuse intracluster light (ICL). Our observations span roughly 16 degrees2 in two filters, reaching a 3 limiting depth of = 29.5 and = 28.5 mag arcsec−2. At these depths, our limiting systematic uncertainties are astrophysical: variations in faint background sources as well as scattered light from galactic dust. We show that this dust-scattered light is well traced by deep far-infrared imaging, making it possible to separate it from true diffuse light in Virgo. We use our imaging to trace and measure the color of the diffuse tidal streams and ICL in the Virgo core near M87, in fields adjacent to the core including the M86/M84 region, and to the south of the core around M49 and subcluster B, along with the more distant W cloud around NGC 4365. Overall, the bulk of the projected ICL is found in the Virgo core and within the W cloud; we find little evidence for an extensive ICL component in the field around M49. The bulk of the ICL we detect is fairly red in color (B − V = 0.7-0.9), indicative of old, evolved stellar populations. Based on the luminosity of the observed ICL features in the cluster, we estimate a total Virgo ICL fraction of 7%-15%. This value is somewhat smaller than that expected for massive, evolved clusters, suggesting that Virgo is still in the process of growing its extended ICL component. We also trace the shape of M87's extremely boxy outer halo out to ∼150 kpc, and show that the current tidal stripping rate from low luminosity galaxies is insufficient to have built M87's outer halo over a Hubble time. We identify a number of previously unknown low surface brightness structures around galaxies projected close to M86 and M84. The extensive diffuse light seen in the infalling W cloud around NGC 4365 is likely to be subsumed in the general Virgo ICL component once the group enters the cluster, illustrating the importance of group infall in generating ICL. Finally, we also identify another large and extremely low surface brightness ultradiffuse galaxy, likely in the process of being shredded by the cluster tidal field. With the survey complete, the full imaging data set is now available for public release.
In The Lancet Oncology, Nicklas Oscarsson and colleagues1 present the results of a randomised, controlled trial reporting the effects of hyperbaric oxygen therapy in the treatment of moderately ...severe radiation-induced cystitis. A Cochrane analysis2 of placebo-controlled trials shows that perception—and not physiological improvement—is at the heart of the placebo effect.2 Another potential criticism is that patients in the control group were allowed to cross over after the primary outcome assessment at 6–8 months after randomisation, and nearly all did so. ...investigators, including myself, have observed that a sizeable proportion of patients treated with hyperbaric oxygen therapy for radiation cystitis will have symptom recurrence even after an apparently adequate course of therapy, but can often be salvaged with additional hyperbaric oxygen treatments.6,7 Long-term follow-up in patients from this study will be essential to establish the durability of response to hyperbaric treatment and the need for additional treatments.
We measure the Balmer decrements of 23 of the brightest planetary nebulae (PNe) in the inner bulge (r 3′) of M31 and deredden the bright end of the region's O iii λ5007 PN luminosity function. We ...show that the most luminous PNe produce 1200 L of power in their O iii λ5007 line, implying central star luminosities of at least ∼11,000 L . Even with the most recent accelerated-evolution post-AGB models, such luminosities require central star masses in excess of 0.66 M and main-sequence progenitors of at least ∼2.5 M . Since M31's bulge has very few intermediate-age stars, we conclude that conventional single-star evolution cannot be responsible for these extremely luminous objects. We also present the circumstellar extinctions for the region's bright PNe and demonstrate that the distribution is similar to that found for PNe in the Large Magellanic Cloud, with a median value of A5007 = 0.71. Finally, we compare our results to extinction measurements made for PNe in the E6 elliptical NGC 4697 and the interacting lenticular NGC 5128. We show that such extinctions are not unusual and that the existence of very high-mass PN central stars is a general feature of old stellar populations. Our results suggest that single-star population synthesis models significantly underestimate the maximum luminosities and total integrated light of AGB stars.
We use deep V-band surface photometry of five of the brightest elliptical galaxies in the Virgo Cluster to search for diffuse tidal streams, shells, and plumes in their outer halos (r>50 kpc). We fit ...and subtract elliptical isophotal models from the galaxy images to reveal a variety of substructure, with surface brightnesses in the range {mu} {sub V} = 26-29 mag arcsec{sup -2}. M49 possesses an extended, interleaved shell system reminiscent of the radial accretion of a satellite companion, while M89's complex system of shells and plumes suggests a more complicated accretion history involving either multiple events or a major merger. M87 has a set of long streamers as might be expected from stripping of low luminosity dwarfs on radial orbits in Virgo. M86 also displays a number of small streams indicative of stripping of dwarf companions, but these comprise much less luminosity than those of M87. Only M84 lacks significant tidal features. We quantify the photometric properties of these structures, and discuss their origins in the context of each galaxy's environment and kinematics within the Virgo Cluster.
SEARCHING FOR DIFFUSE LIGHT IN THE M96 GALAXY GROUP Watkins, Aaron E; Mihos, J Christopher; Harding, Paul ...
Astrophysical journal/The Astrophysical journal,
08/2014, Volume:
791, Issue:
1
Journal Article
Peer reviewed
Open access
We present deep, wide-field imaging of the M96 galaxy group (also known as the Leo I Group). Down to surface brightness limits of mu sub(B) = 30.1 and mu sub(V) = 29.5, we find no diffuse, ...large-scale optical counterpart to the "Leo Ring," an extended H I ring surrounding the central elliptical M105 (NGC 3379). However, we do find a number of extremely low surface brightness ( mu sub(B) gap 29) small-scale streamlike features, possibly tidal in origin, two of which may be associated with the Ring. In addition, we present detailed surface photometry of each of the group's most massive members-M105, NGC 3384, M96 (NGC 3368), and M95 (NGC 3351)-out to large radius and low surface brightness, where we search for signatures of interaction and accretion events. We find that the outer isophotes of both M105 and M95 appear almost completely undisturbed, in contrast to NGC 3384 which shows a system of diffuse shells indicative of a recent minor merger. We also find photometric evidence that M96 is accreting gas from the H I ring, in agreement with H I data. In general, however, interaction signatures in the M96 Group are extremely subtle for a group environment, and provide some tension with interaction scenarios for the formation of the Leo H I Ring. The lack of a significant component of diffuse intragroup starlight in the M96 Group is consistent with its status as a loose galaxy group in which encounters are relatively mild and infrequent.
We use deep Hubble Space Telescope imaging in the outskirts of the nearby spiral M101 to study stellar populations in the galaxy's outer disk and halo. Our Advanced Camera for Surveys (ACS) field ...lies 17 6 (36 kpc) from the center of M101 and targets the blue "NE Plume" of M101's outer disk, while the parallel Wide Field Camera 3 (WFC3) field lies at a distance of 23 3 (47 kpc) to sample the galaxy's stellar halo. The WFC3 halo field shows a well-defined red giant branch characterized by low metallicity (M/H = −1.7 0.2), with no evidence of young stellar populations. In contrast, the ACS disk field shows multiple stellar populations, including a young main sequence, blue and red helium-burning stars, and old RGB and asymptotic giant branch (AGB) populations. The mean metallicity of these disk stars is quite low: M/H = −1.3 0.2 for the RGB population, and −1.15 0.2 for the younger helium-burning sequences. Of particular interest is a bunching of stars along the BHeB sequence, indicative of an evolving cohort of massive young stars. We show that the young stellar populations in this field are well-described by a decaying burst of star formation that peaked ∼300-400 Myr ago, along with a more extended star formation history to produce the older RGB and AGB populations. These results confirm and extend the results from our previous deep surface photometry of M101's outer disk, providing an important cross-check on stellar population studies using resolved stellar populations versus integrated light photometry. We discuss our results in the context of halo formation models and the interaction history of M101 and its companions.
Informal surveys at CME meetings have shown that approximately one-third of patients in the United States receive hyperbaric oxygen (HBO2) for delayed radiation injury. More than 600,000 patients ...receive radiation for malignancy in our country annually, and about one-half will be long-term survivors. Serious radiation complications occur in 5-10% of survivors. A large population of patients is therefore at risk for radiation injury. HBO2 has been applied to treat patients with radiation injury since the mid-1970s. Published results are consistently positive, but the level of evidence for individual publications is usually not high level, consisting mostly of case series and case reports. Only a rare randomized controlled trial has been accomplished. Radiation injury is one of the UHMS "approved" indications, and third-party payors will usually reimburse for this application. This updated review summarizes the publications available reporting results in treating radiation-injured patients. Mechanisms of HBO2 in radiation injury are discussed briefly. Outcome is reported on a mostly anatomic basis though due to the nature of the injury a positive outcome at one anatomic site is supportive of HBO2 at other sites. The potential benefit of prophylactic HBO2 before frank damage is also discussed in high-risk patients. The concerns of HBO2 enhancing growth of or precipitating recurrence of malignancy is discussed and largely refuted.
Abstract
The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) is an untargeted spectroscopic survey that aims to measure the expansion rate of the universe at
z
∼ 2.4 to 1% precision for both
H
...(
z
) and
D
A
(
z
). HETDEX is in the process of mapping in excess of one million Ly
α
emitting (LAE) galaxies and a similar number of lower-
z
galaxies as a tracer of the large-scale structure. The success of the measurement is predicated on the post-observation separation of galaxies with Ly
α
emission from the lower-
z
interloping galaxies, primarily O
ii
, with low contamination and high recovery rates. The Emission Line eXplorer (ELiXer) is the principal classification tool for HETDEX, providing a tunable balance between contamination and completeness as dictated by science needs. By combining multiple selection criteria, ELiXer improves upon the 20 Å rest-frame equivalent width cut commonly used to distinguish LAEs from lower-
z
O
ii
emitting galaxies. Despite a spectral resolving power,
R
∼ 800, that cannot resolve the O
ii
doublet, we demonstrate the ability to distinguish LAEs from foreground galaxies with 98.1% accuracy. We estimate a contamination rate of Ly
α
by O
ii
of 1.2% and a Ly
α
recovery rate of 99.1% using the default ELiXer configuration. These rates meet the HETDEX science requirements.
As the first step to determine disk mass-to-light ratios for normal spiral galaxies, we present the results of an imaging survey for planetary nebulae (PNe) in six nearby, face-on systems: IC 342, ...M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), NGC 5068, and NGC 6946. Using Blanco/Mosaic II and WIYN/OPTIC, we identify 165, 153, 241, 150, 19, and 71 PN candidates, respectively, and use the planetary nebula luminosity function (PNLF) to obtain distances. For M74 and NGC 5068, our distances of image and image Mpc are the first reliable estimates to these objects; for IC 342 (image Mpc), M83 (image Mpc), M94 (image Mpc), and NGC 6946 (image Mpc) our values agree well with those in the literature. In the larger systems, we find no evidence for any systematic change in the PNLF with galactic position, although we do see minor field-to-field variations in the luminosity function. In most cases, these changes do not affect the measurement of distance, but in one case the fluctuations result in a image0.2 mag shift in the location of the PNLF cutoff. We discuss the possible causes of these small-scale changes, including internal extinction in the host galaxies and age/metallicity changes in the underlying stellar population.
We studied the clustering properties and multiwavelength spectral energy distributions of a complete sample of 162 Ly alpha -emitting (LAE) galaxies at z unk 3.1 discovered in deep narrowband MUSYC ...imaging of the Extended Chandra Deep Field-South. LAEs were selected to have observed frame equivalent widths >80 AAA and emission line fluxes >1.5 x 10 super(-17) ergs cm super(-2) s super(-1). Only 1% of our LAE sample appears to host AGNs. The LAEs exhibit a moderate spatial correlation length of unk = unk Mpc, corresponding to a bias factor b = unk, which implies median dark matter halo masses of log sub(10)M unk = unk M unk. Comparing the number density of LAEs, 1.5 plus or minus 0.3 x 10 super(-3) Mpc super(-3), with the number density of these halos finds a mean halo occupation similar to 1%-10%. The evolution of galaxy bias with redshift implies that most z = 3.1 LAEs evolve into present-day galaxies with unk, whereas other z > 3 galaxy populations typically evolve into more massive galaxies. Halo merger trees show that z = 0 descendants occupy halos with a wide range of masses, with a median descendant mass close to that of unk. Only 30% of LAEs have sufficient stellar mass (> similar to 3 x unk M unk) to yield detections in deep Spitzer IRAC imaging. A two-population SED fit to the stacked UBVRIzJK+3.6, 4.5, 5.6, 8.0 mu m fluxes of the IRAC-undetected objects finds that the typical LAE has low stellar mass ( unk x unk M unk), moderate star formation rate (2 plus or minus 1 M unk yr super(-1)), a young component age of unk Myr, and little dust (Av < 0.2). The best-fit model has 20% of the mass in the young stellar component, but models without evolved stars are also allowed.
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