Search

We present the discovery of DELVE 6, an ultra-faint stellar system identified in the second data release of the DECam Local Volume Exploration (DELVE) survey. Based on a maximum-likelihood fit to its structure and stellar population, we find that DELVE 6 is an old ( τ > 9.8 Gyr at 95% confidence) and metal-poor ([Fe/H] < −1.17 dex at 95% confidence) stellar system with an absolute magnitude of ${M}_{V}=-{1.5}_{-0.6}^{+0.4}$ mag and an azimuthally averaged half-light radius of ${r}_{1/2}={10}_{-3}^{+4}$ pc. These properties are consistent with the population of ultra-faint star clusters uncovered by recent surveys. Interestingly, DELVE 6 is located at an angular separation of ∼10° from the center of the Small Magellanic Cloud (SMC), corresponding to a 3D physical separation of ∼20 kpc given the system’s observed distance ( D _⊙ = 80 kpc). This also places the system ∼35 kpc from the center of the Large Magellanic Cloud (LMC), lying within recent constraints on the size of the LMC’s dark matter halo. We tentatively measure the proper motion of DELVE 6 using data from Gaia, which we find supports a potential association between the system and the LMC/SMC. Although future kinematic measurements will be necessary to determine its origins, we highlight that DELVE 6 may represent only the second or third ancient ( τ > 9 Gyr) star cluster associated with the SMC, or one of fewer than two dozen ancient clusters associated with the LMC. Nonetheless, we cannot currently rule out the possibility that the system is a distant Milky Way halo star cluster.

We report the discovery of Pegasus IV, an ultra-faint dwarf galaxy found in archival data from the Dark Energy Camera processed by the DECam Local Volume Exploration Survey. Pegasus IV is a compact, ultra-faint stellar system ( ${r}_{1/2}={41}_{-6}^{+8}$ pc; M _V = −4.25 ± 0.2 mag) located at a heliocentric distance of ${90}_{-6}^{+4}\,\mathrm{kpc}$ . Based on spectra of seven nonvariable member stars observed with Magellan/IMACS, we confidently resolve Pegasus IV’s velocity dispersion, measuring ${\sigma }_{v}={3.3}_{-1.1}^{+1.7}$ km s ^−1 (after excluding three velocity outliers); this implies a mass-to-light ratio of ${M}_{1/2}/{L}_{V,1/2}={167}_{-99}^{+224}{M}_{\odot }/{L}_{\odot }$ for the system. From the five stars with the highest signal-to-noise spectra, we also measure a systemic metallicity of [Fe/H] = $-{2.63}_{-0.30}^{+0.26}$ dex, making Pegasus IV one of the most metal-poor ultra-faint dwarfs. We tentatively resolve a nonzero metallicity dispersion for the system. These measurements provide strong evidence that Pegasus IV is a dark-matter-dominated dwarf galaxy, rather than a star cluster. We measure Pegasus IV’s proper motion using data from Gaia Early Data Release 3, finding ( μ _α _* , μ _δ ) = (0.33 ± 0.07, −0.21 ± 0.08) mas yr ^−1 . When combined with our measured systemic velocity, this proper motion suggests that Pegasus IV is on an elliptical, retrograde orbit, and is currently near its orbital apocenter. Lastly, we identify three potential RR Lyrae variable stars within Pegasus IV, including one candidate member located more than 10 half-light radii away from the system’s centroid. The discovery of yet another ultra-faint dwarf galaxy strongly suggests that the census of Milky Way satellites is still incomplete, even within 100 kpc.

We report the discovery of two ultra-faint stellar systems found in early data from the DECam Local Volume Exploration survey (DELVE). The first system, Centaurus I (DELVE J1238–4054), is identified as a resolved overdensity of old and metal-poor stars with a heliocentric distance of , a half-light radius of , an age of , a metallicity of , and an absolute magnitude of . This characterization is consistent with the population of ultra-faint satellites and confirmation of this system would make Centaurus I one of the brightest recently discovered ultra-faint dwarf galaxies. Centaurus I is detected in Gaia DR2 with a clear and distinct proper motion signal, confirming that it is a real association of stars distinct from the Milky Way foreground; this is further supported by the clustering of blue horizontal branch stars near the centroid of the system. The second system, DELVE 1 (DELVE J1630–0058), is identified as a resolved overdensity of stars with a heliocentric distance of , a half-light radius of , an age of , a metallicity of , and an absolute magnitude of , consistent with the known population of faint halo star clusters. Given the low number of probable member stars at magnitudes accessible with Gaia DR2, a proper motion signal for DELVE 1 is only marginally detected. We compare the spatial position and proper motion of both Centaurus I and DELVE 1 with simulations of the accreted satellite population of the Large Magellanic Cloud (LMC) and find that neither is likely to be associated with the LMC. [ABSTRACT FROM AUTHOR]

We cross-match high-precision astrometric data from Gaia DR2 with accurate multiband photometry from the Dark Energy Survey (DES) DR1 to confidently measure proper motions for nine stellar streams in the DES footprint: Aliqa Uma, ATLAS, Chenab, Elqui, Indus, Jhelum, Phoenix, Tucana III, and Turranburra. We determine low-confidence proper-motion measurements for four additional stellar streams: Ravi, Wambelong, Willka Yaku, and Turbio. We find evidence for a misalignment between stream tracks and the systemic proper motion of streams that may suggest a systematic gravitational influence from the Large Magellanic Cloud (LMC). These proper motions, when combined with radial velocity measurements, will allow for detailed orbit modeling that can be used to constrain properties of the LMC and its effect on nearby streams, as well as global properties of the Milky Way’s gravitational potential. [ABSTRACT FROM AUTHOR]

We present a spectroscopic study of the tidal tails and core of the Milky Way satellite Tucana III, collectively referred to as the Tucana III stream, using the 2dF+AAOmega spectrograph on the Anglo-Australian Telescope and the IMACS spectrograph on the Magellan Baade Telescope. In addition to recovering the brightest nine previously known member stars in the Tucana III core, we identify 22 members in the tidal tails. We observe strong evidence for a velocity gradient of over at least 3° on the sky. Based on the continuity in velocity, we confirm that the Tucana III tails are real tidal extensions of Tucana III. The large velocity gradient of the stream implies that Tucana III is likely on a radial orbit. We successfully obtain metallicities for four members in the core and 12 members in the tails. We find that members close to the ends of the stream tend to be more metal-poor than members in the core, indicating a possible metallicity gradient between the center of the progenitor halo and its edge. The spread in metallicity suggests that the progenitor of the Tucana III stream is likely a dwarf galaxy rather than a star cluster. Furthermore, we find that with the precise photometry of the Dark Energy Survey data, there is a discernible color offset between metal-rich disk stars and metal-poor stream members. This metallicity-dependent color offers a more efficient method to recognize metal-poor targets and will increase the selection efficiency of stream members for future spectroscopic follow-up programs on stellar streams. [ABSTRACT FROM AUTHOR]

We perform a search for stellar streams around the Milky Way using the first 3 yr of multiband optical imaging data from the Dark Energy Survey (DES). We use DES data covering ∼5000 deg2 to a depth of g > 23.5 with a relative photometric calibration uncertainty of <1%. This data set yields unprecedented sensitivity to the stellar density field in the southern celestial hemisphere, enabling the detection of faint stellar streams to a heliocentric distance of ∼50 kpc. We search for stellar streams using a matched filter in color–magnitude space derived from a synthetic isochrone of an old, metal-poor stellar population. Our detection technique recovers four previously known thin stellar streams: Phoenix, ATLAS, Tucana III, and a possible extension of Molonglo. In addition, we report the discovery of 11 new stellar streams. In general, the new streams detected by DES are fainter, more distant, and lower surface brightness than streams detected by similar techniques in previous photometric surveys. As a by-product of our stellar stream search, we find evidence for extratidal stellar structure associated with four globular clusters: NGC 288, NGC 1261, NGC 1851, and NGC 1904. The ever-growing sample of stellar streams will provide insight into the formation of the Galactic stellar halo, the Milky Way gravitational potential, and the large- and small-scale distribution of dark matter around the Milky Way. [ABSTRACT FROM AUTHOR]

Background: Chemoembolization with small drug-eluting microspheres is widely used in the treatment of hepatocellular carcinoma (HCC)., Objectives: This study aimed to evaluate the efficacy and safety of transarterial chemoembolization with doxorubicin-eluting 30-60-µm microspheres (DEB-TACE) in patients with Barcelona Clinic Liver Cancer (BCLC) stage A and B HCC., Materials and Methods: In this single-center study, 88 patients with HCC (BCLC A/B: 15.9%/84.1%) who underwent 137 DEB-TACE sessions between January 2015 and December 2020 were retrospectively assessed. Response to treatment was assessed 4-8 weeks after each DEB-TACE procedure according to mRECIST (Modified Response Evaluation Criteria in Solid Tumors) criteria. Progression-free survival (PFS), time to progression (TTP), overall survival (OS), and adverse events were recorded., Results: In 88 patients (84.1% males; median age, 66.0 years; range, 22-83), the median follow-up was 17 months (range, 2-64). Eight patients (9.1%) had a complete response, 42 (47.8%) had partial regression, 10 (11.3%) had stable disease, and 28 (31.8%) had progressive disease. There was a statistically significant difference between serum alpha-fetoprotein (AFP) levels before and after DEB-TACE treatment (p < 0.001). The median OS was 17 months (95% confidence interval [CI], 10.3-23.7). Cox regression analyses found that preprocedural serum AFP level (400+ vs. < 400; p = 0.024), Child Pugh classification (B vs. A; p = 0.019), and number of DEB-TACE sessions (1 vs. > 1; p = 0.003) were independent risk factors affecting OS. The median PFS was 8 months (95% CI, 5.8-10.2) and TTP was 6 months (1-14 months)., Conclusion: Chemoembolization with 30-60-µm microspheres is an effective and safe treatment for HCC. The number of DEB-TACE sessions is also one of the factors affecting OS., (© 2024. The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

Background: Fat quantification methods in magnetic resonance imaging (MRI) have been studied to differentiate bone marrow pathologies in adult patients; however, scarce literature is available in pediatric patients., Purpose: To evaluate the efficacy of the T1 signal intensity value (T1-SIV), out-of-phase/in-phase signal ratio (OP/IP SR), and fat fraction (FF) to differentiate between normal, benign, and malignant pathological processes., Material and Methods: A total of 48 pediatric patients with lumbar and pelvic MRI were classified into three groups according to bone marrow pathology (group 1, normal; group 2, benign pathology/reconversion; group 3, malignant). The efficacy of T1-SIV, OP/IP SR, and FF values in differentiating these pathologies was evaluated using Kruskal-Wallis or analysis of variance and followed by Bonferroni or Dunn-Bonferroni tests. Cutoff values for malignant infiltration were defined using ROC analysis., Results: Although these values were significantly different in all three groups ( P  = 0.001-0.008), this difference was not sufficient to discriminate between all groups. Subgroup analyses showed significant differences in T1-SIV between groups 1-3, in OP/IP SR between groups 1-3, 2-3, and 1-2, in FF between groups 1-2 and 1-3 in various regions ( P  = 0.001-0.049). Cutoff values had a sensitivity and specificity of 90%-100% for OP/IP SR and FF., Conclusion: T1-SIV, OP/IP SR, and FF may potentially distinguish normal from pathological bone marrow. OP/IP SR and FF values detected malignant infiltration with high sensitivity and specificity in this study. However, only OP/IP SR may significantly differentiate benign and malignant bone marrow pathologies which needs to be confirmed in the future study with a larger patient population., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Purpose: The aim of this study was to evaluate the diagnostic performance of Inhance 3D Velocity (I3DV) in intracranial venous thrombosis and investigate the possible impact of venous sinus hypoplasia/aplasia on false thrombosis diagnosis made with I3DV., Methods: This study included 540 patients. Contrast-enhanced magnetic resonance venography combined with conventional sequences was considered the gold standard test (GST), while I3DV was considered as diagnostic test. We accessed the diagnostic success of I3DV for intracranial venous thrombosis detection, thrombosed vessel identification, and total/partial thrombus distinction. The possible relationship between false-positive thrombus diagnosed by I3DV and venous sinus hypoplasia or aplasia diagnosed by GST was investigated., Results: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of I3DV in the detection of intracranial venous thrombosis were 95.7%, 92.1%, 64.1%, 99.3%, and 92.6%, respectively. A significant association was observed between I3DV and GST in terms of thrombosis detection and total/partial thrombus distinction (p < 0.001). A significant relationship was observed between false-positive thrombosis diagnosis in I3DV and hypoplasia in the left transverse sinus (p < 0.001)., Conclusion: Intracranial venous thrombosis may be diagnosed faster and more accurately than traditional phase contrast magnetic resonance angiography in I3DV. This technique can be used in situations where contrast medium application is contraindicated. As in other non-contrast magnetic resonance venography techniques, left transverse sinus hypoplasia can be diagnosed as a thrombosed vessel in I3DV., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In this article, we present a case of leptomeningeal pneumocephalus and pneumorrhachis secondary to pneumothorax that occurred six years after syringopleural shunting., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Globular clusters are some of the oldest bound stellar structures observed in the Universe 1 . They are ubiquitous in large galaxies and are believed to trace intense star-formation events and the hierarchical build-up of structure 2,3 . Observations of globular clusters in the Milky Way, and a wide variety of other galaxies, have found evidence for a 'metallicity floor', whereby no globular clusters are found with chemical (metal) abundances below approximately 0.3 to 0.4 per cent of that of the Sun 4-6 . The existence of this metallicity floor may reflect a minimum mass and a maximum redshift for surviving globular clusters to form-both critical components for understanding the build-up of mass in the Universe 7 . Here we report measurements from the Southern Stellar Streams Spectroscopic Survey of the spatially thin, dynamically cold Phoenix stellar stream in the halo of the Milky Way. The properties of the Phoenix stream are consistent with it being the tidally disrupted remains of a globular cluster. However, its metal abundance ([Fe/H] = -2.7) is substantially below the empirical metallicity floor. The Phoenix stream thus represents the debris of the most metal-poor globular clusters discovered so far, and its progenitor is distinct from the present-day globular cluster population in the local Universe. Its existence implies that globular clusters below the metallicity floor have probably existed, but were destroyed during Galactic evolution.