We have obtained deep Hubble Space Telescope (HST) imaging of 19 dwarf galaxy candidates in the vicinity of M101. Advanced Camera for Surveys HST photometry for two of these objects showed resolved ...stellar populations and tip of the red giant branch derived distances (D ∼ 7 Mpc) consistent with M101 group membership. The remaining 17 were found to have no resolved stellar populations, meaning they are either part of the background NGC 5485 group or are distant low surface brightness (LSB) galaxies. It is noteworthy that many LSB objects that had previously been assumed to be M101 group members based on projection have been shown to be background objects, indicating the need for future diffuse dwarf surveys to be very careful in drawing conclusions about group membership without robust distance estimates. In this work we update the satellite luminosity function of M101 based on the presence of these new objects down to MV = −8.2. M101 is a sparsely populated system with only nine satellites down to MV −8, as compared with 26 for M31 and 24.5 7.7 for the median host in the Local Volume. This makes M101 by far the sparsest group probed to this depth, although M94 is even sparser to the depth at which it has been examined (MV = −9.1). M101 and M94 share several properties that mark them as unusual compared with the other Local Volume galaxies examined: they have a very sparse satellite population but also have high star-forming fractions among these satellites; such properties are also found in the galaxies examined as part of the Satellites around Galactic Analogs survey. We suggest that these properties appear to be tied to the wider galactic environment, with more isolated galaxies showing sparse satellite populations that are more likely to have had recent star formation, while those in dense environments have more satellites that tend to have no ongoing star formation. Overall, our results show a level of halo-to-halo scatter between galaxies of similar mass that is larger than is predicted in the lambda cold dark matter model.
We present the widest-field resolved stellar map to date of the closest (D~ 3.8 Mpc) massive elliptical galaxy NGC 5128 (Centaurus A; Cen A), extending out to a projected galactocentric radius of ...~150 kpc. The data set is part of our ongoing Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) utilizing the Magellan/Megacam imager. We resolve a population of old red giant branch (RGB) stars down to ~1.5 mag below the tip of the RGB, reaching surface brightness limits as low as muv,0~ 32 mag arcsec super(-2). The resulting spatial stellar density map highlights a plethora of previously unknown streams, shells, and satellites, including the first tidally disrupting dwarf around Cen A (CenA-MM-Dw3), which underline its active accretion history. We report 13 previously unknown dwarf satellite candidates, of which 9 are confirmed to be at the distance of Cen A (the remaining 4 are not resolved into stars), with magnitudes in the range Mv=-7.2 to -13.0, central surface brightness values of muv,0= 25.4-26.9 mag arcsec super(-2), and half-light radii of rh= 0.22-2.92 kpc. These values are in line with Local Group dwarfs but also lie at the faint/diffuse end of their distribution; interestingly, CenA-MM-Dw3 has similar properties to the recently discovered ultradiffuse galaxies in Virgo and Coma. Most of the new dwarfs are fainter than the previously known Cen A satellites. The newly discovered dwarfs and halo substructures are discussed in light of their stellar populations, and they are compared to those discovered by the PAndAS survey of M31.
We have conducted a search of a 9 deg2 region of the Canada-France-Hawaii-Telescope Legacy Survey around the Milky Way analog M101 (D ∼ 7 Mpc), in order to look for previously unknown ...low-surface-brightness galaxies. This search has uncovered 38 new low-surface-brightness dwarf candidates, and confirmed 11 previously reported galaxies, all with central surface brightness (g, 0) > 23 mag arcsec−2, potentially extending the satellite luminosity function for the M101 group by ∼1.2 mag. The search was conducted using an algorithm that nearly automates the detection of diffuse dwarf galaxies. The candidates' small sizes and low surface brightnesses mean that the faintest of these objects would likely be missed by traditional visual or computer detection techniques. The dwarf galaxy candidates span a range of −7.1 ≥ Mg ≥ −10.2 and half-light radii of 118-540 pc at the distance of M101, and they are well fit by simple Sérsic surface brightness profiles. These properties are consistent with dwarfs in the Local Group, and to match the Local Group luminosity function, ∼10-20 of these candidates should be satellites of M101. Association with a massive host is supported by the lack of detected star formation and the overdensity of candidates around M101 compared to the field. The spatial distribution of the dwarf candidates is highly asymmetric, and concentrated to the northeast of M101, therefore distance measurements will be required to determine if these are genuine members of the M101 group.
Summary
Background Perturbations in the expression profiles of microRNAs (miRNAs) have been reported for a variety of different cancers. Differentially expressed miRNAs have not been systematically ...evaluated in basal cell carcinoma (BCC) of the skin.
Objectives To initiate a microarray‐based miRNA profiling study to identify specific miRNA candidates that are differentially expressed in BCC.
Methods Patients with BCC (n = 7) were included in this study. Punch biopsies were harvested from the tumour centre (lesional, n = 7) and from adjacent nonlesional skin (intraindividual control, n = 7). Microarray‐based miRNA expression profiles were obtained on an Agilent platform using miRBase 16 screening for 1205 Homo sapiens (hsa)‐miRNA candidates. To validate the microarray data, the expression of seven dysregulated miRNAs was measured by TaqMan quantitative real‐time reverse transcription polymerase chain reaction.
Results We identified 16 significantly upregulated (hsa‐miR‐17, hsa‐miR‐18a, hsa‐miR‐18b, hsa‐miR‐19b, hsa‐miR‐19b‐1*, hsa‐miR‐93, hsa‐miR‐106b, hsa‐miR‐125a‐5p, hsa‐miR‐130a, hsa‐miR‐181c, hsa‐miR‐181c*, hsa‐miR‐181d, hsa‐miR‐182, hsa‐miR‐455‐3p, hsa‐miR‐455‐5p and hsa‐miR‐542‐5p) and 10 significantly downregulated (hsa‐miR‐29c, hsa‐miR‐29c*, hsa‐miR‐139‐5p, hsa‐miR‐140‐3p, hsa‐miR‐145, hsa‐miR‐378, hsa‐miR‐572, hsa‐miR‐638, hsa‐miR‐2861 and hsa‐miR‐3196) miRNAs in BCC compared with nonlesional skin. Data mining revealed connections to many tumour‐promoting pathways, such as the Hedgehog and the mitogen‐activated protein kinase/extracellular signal‐regulated kinase signalling cascades.
Conclusions This study identified several miRNA candidates that may play a role in the molecular pathogenesis of BCC.
Abstract
We present late-time spectra of eight Type Ia supernovae (SNe Ia) obtained at >200 d after peak brightness using the Gemini South and Keck telescopes. All of the SNe Ia in our sample were ...nearby, well separated from their host galaxy's light, and have early-time photometry and spectroscopy from the Las Cumbres Observatory. Parameters are derived from the light curves and spectra such as peak brightness, decline rate, photospheric velocity and the widths and velocities of the forbidden nebular emission lines. We discuss the physical interpretations of these parameters for the individual SNe Ia and the sample in general, including comparisons to well-observed SNe Ia from the literature. There are possible correlations between early-time and late-time spectral features that may indicate an asymmetric explosion, so we discuss our sample of SNe within the context of models for an offset ignition and/or white dwarf collisions. A subset of our late-time spectra are uncontaminated by host emission, and we statistically evaluate our non-detections of H α emission to limit the amount of hydrogen in these systems. Finally, we consider the late-time evolution of the iron emission lines, finding that not all of our SNe follow the established trend of a redward migration at >200 d after maximum brightness.
We report the discovery of two ultra-diffuse galaxies (UDGs) that show clear evidence of an association with tidal material and an interaction with a larger galaxy halo, found during a search of the ...Wide portion of the Canada-France-Hawaii Telescope Legacy Survey. The two new UDGs, NGC 2708-Dw1 and NGC 5631-Dw1, are faint (Mg = −13.7 and −11.8 mag), extended (rh = 2.60 and 2.15 kpc), and have low central surface brightness ( (g, 0) = 24.9 and 27.3 mag arcsec−2), while the stellar stream associated with each has a surface brightness (g) 28.2 mag arcsec−2. These observations provide evidence that the origin of some UDGs may connect to galaxy interactions, either by transforming normal dwarf galaxies by expanding them, or because UDGs can collapse out of tidal material (i.e., they are tidal dwarf galaxies). Further work is needed to understand the fraction of the UDG population "formed" through galaxy interactions, and wide field searches for diffuse dwarf galaxies will provide further clues to the origin of these enigmatic stellar systems.
SN 2014J in M82 is the closest detected Type Ia supernova (SN Ia) in at least 28 yr and perhaps in 410 yr. Despite its small distance of 3.3 Mpc, SN 2014J is surprisingly faint, peaking at ...V = 10.6 mag, and assuming a typical SN Ia luminosity, we infer an observed visual extinction of A
V
= 2.0 ± 0.1 mag. But this picture, with R
V
= 1.6 ± 0.2, is too simple to account for all observations. We combine 10 epochs (spanning a month) of HST/Space Telescope Imaging Spectrograph (STIS) ultraviolet through near-infrared spectroscopy with HST/Wide Field Camera 3 (WFC3), Katzman Automatic Imaging Telescope, and FanCam photometry from the optical to the infrared and nine epochs of high-resolution TRES (Tillinghast Reflection Echelle Spectrograph) spectroscopy to investigate the sources of extinction and reddening for SN 2014J. We argue that the wide range of observed properties for SN 2014J is caused by a combination of dust reddening, likely originating in the interstellar medium of M82, and scattering off circumstellar material. For this model, roughly half of the extinction is caused by reddening from typical dust (E(B − V) = 0.45 mag and R
V
= 2.6) and roughly half by scattering off Large Magellanic Cloud-like dust in the circumstellar environment of SN 2014J.
We present a revised and complete optical afterglow light curve of the binary neutron star merger GW170817, enabled by deep Hubble Space Telescope (HST) F606W observations at 584 days post-merger, ...which provide a robust optical template. The light curve spans 110-362 days, and is fully consistent with emission from a relativistic structured jet viewed off-axis, as previously indicated by radio and X-ray data. Combined with contemporaneous radio and X-ray observations, we find no spectral evolution, with a weighted average spectral index of 〈 β 〉 = − 0.583 0.013 , demonstrating that no synchrotron break frequencies evolve between the radio and X-ray bands over these timescales. We find that an extrapolation of the post-peak temporal slope of GW170817 to the luminosities of cosmological short gamma-ray bursts matches their observed jet break times, suggesting that their explosion properties are similar, and that the primary difference in GW170817 is viewing angle. Additionally, we place a deep limit on the luminosity and mass of an underlying globular cluster (GC) of L 6.7 × 103 L , or M 1.3 × 104 M , at least 4 standard deviations below the peak of the GC mass function of the host galaxy, NGC 4993. This limit provides a direct and strong constraint that GW170817 did not form and merge in a GC. As highlighted here, HST (and soon the James Webb Space Telescope) enables critical observations of the optical emission from neutron star merger jets and outflows.
We study the optical light curve (LC) relations of Type Ia supernovae (SNe Ia) for their use in cosmology using high-quality photometry published by the Carnegie Supernova Project (CSP-I). We revisit ...the classical luminosity decline rate (Δm15) relation and the Lira relation, as well as investigate the time evolution of the (B − V) color and B(B − V), which serves as the basis of the color-stretch relation and Color-MAgnitude Intercept Calibrations (CMAGIC). Our analysis is based on explosion and radiation transport simulations for spherically symmetric delayed-detonation models (DDT) producing normal-bright and subluminous SNe Ia. Empirical LC relations can be understood as having the same physical underpinnings, i.e., opacities, ionization balances in the photosphere, and radioactive energy deposition changing with time from below to above the photosphere. Some three to four weeks past maximum, the photosphere recedes to 56Ni-rich layers of similar density structure, leading to a similar color evolution. An important secondary parameter is the central density c of the WD because at higher densities, more electron-capture elements are produced at the expense of 56Ni production. This results in a Δm15 spread of 0.1 mag in normal-bright and 0.7 mag in subluminous SNe Ia and 0.2 mag in the Lira relation. We show why color-magnitude diagrams emphasize the transition between physical regimes and enable the construction of templates that depend mostly on Δm15 with little dispersion in both the CSP-I sample and our DDT models. This allows intrinsic SN Ia variations to be separated from the interstellar reddening characterized by E(B − V) and RB. Invoking different scenarios causes a wide spread in empirical relations, which may suggest one dominant scenario.
We present proper motion (PM) measurements of Boötes III, an enigmatic stellar satellite of the Milky Way (MW), utilizing data from the second data release of the Gaia mission. By selecting 15 radial ...velocity confirmed members of Boötes III, along with a likely RR Lyrae member in the vicinity, we measure an error-weighted mean PM of ( , δ) = (−1.14, −0.98) (0.18, 0.20) mas yr−1. We select and present further stars that may be Boötes III members based on their combined PM and position in the color-magnitude diagram. We caution against assigning membership to stars that are not confirmed spectroscopically, as we demonstrate that there are contaminating stars from the disrupting globular cluster NGC 5466 in the vicinity of the main body of Boötes III, but we note that our results are consistent with previous Boötes III PM estimates that did not include spectroscopic members. Based on the measured PM and other known properties of Boötes III, we derive its Galactocentric velocity and compute its orbit given canonical MW potentials with halo masses of both 0.8 × 1012 M and 1.6 × 1012 M . These orbits robustly show that Boötes III passed within ∼12 kpc of the Galactic center on an eccentric orbit roughly ∼140 Myr ago. Additionally, the PM of Boötes III is in excellent agreement with predictions for the retrograde motion of the coincident Styx stellar stream. Given this, along with the small pericenter and metallicity spread of Boötes III itself, we suggest that it is a disrupting dwarf galaxy giving rise to the Styx stellar stream.
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