We present Hubble Space Telescope (HST) observations of the low surface brightness (SB) galaxy Coma P. This system was first discovered in the Arecibo Legacy Fast ALFA H I survey and was cataloged as an (almost) dark galaxy because it did not exhibit any obvious optical counterpart in the available survey data (e.g., Sloan Digital Sky Survey). Subsequent WIYN pODI imaging revealed an ultra-low SB stellar component located at the center of the H I detection. We use the HST images to produce a deep color-magnitude diagram (CMD) of the resolved stellar population present in Coma P. We clearly detect a red stellar sequence that we interpret to be a red giant branch, and use it to infer a tip of the red giant branch (TRGB) distance of 5.50 +0.28 −0.53 Mpc. The new distance is substantially lower than earlier estimates and shows that Coma P is an extreme dwarf galaxy. Our derived stellar mass is only 4.3 × 10 5 M , meaning that Coma P has an extreme H I-to-stellar mass ratio of 81. We present a detailed analysis of the galaxy environment within which Coma P resides. We hypothesize that Coma P formed within a local void and has spent most of its lifetime in a low-density environment. Over time, the gravitational attraction of the galaxies located in the void wall has moved it to the edge, where it had a recent "fly-by" interaction with M64. We investigate the possibility that Coma P is at a farther distance and conclude that the available data are best fit by a distance of 5.5 Mpc.

We present new high-resolution H I spectral line imaging of Coma P, the brightest H I source in the system HI 1232 +20. This galaxy with extremely low surface brightness was first identified in the ALFALFA survey as an "(Almost) Dark" object: a clearly extragalactic H I source with no obvious optical counterpart in existing optical survey data (although faint ultraviolet emission was detected in archival GALEX imaging). Using a combination of data from the Westerbork Synthesis Radio Telescope and the Karl G. Jansky Very Large Array, we investigate the H I morphology and kinematics at a variety of physical scales. The H I morphology is irregular, reaching only moderate maxima in mass surface density (peak M 10 H I s~ pc −2 ). Gas of lower surface brightness extends to large radial distances, with the H I diameter measured at 4.0±0.2 kpc inside the M 1  pc −2 level. We quantify the relationships between mass surface density of H I gas and star formation on timescales of ∼100-200 Myr as traced by GALEX far-ultraviolet emission. While Coma P has regions of dense H I gas reaching the N 10 I I scaling relation. It is either too large for its H I mass, has too low an H I mass for its H I size, or the two H I components artificially extend its H I size. Coma P lies within the empirical scatter at the faint end of the baryonic Tully-Fisher relation, although the complexity of the H I dynamics complicates the interpretation. Along with its large ratio of H I to stellar mass, the collective H I characteristics of Coma P make it unusual among known galaxies in the nearby universe.

The nitrogen-to-oxygen (N/O) abundance ratio is an important diagnostic of galaxy evolution because the ratio is closely tied to the growth of metallicity and the star formation history in galaxies. Estimates for the N/O are traditionally made with optical lines that could suffer from extinction and excitation effects, so the N/O is arguably measured better through far-infrared (far-IR) fine-structure lines. Here we show that the [N iii]57 μm/[O iii]52 μm line ratio, denoted N3O3, is a physically robust probe of N/O. This parameter is insensitive to gas temperature and only weakly dependent on electron density. Although it has a dependence on the hardness of the ionizing radiation field, we show that it is well corrected when the [Ne iii]15.5 μm/[Ne ii]12.8 μm line ratio is included. We verify the method, and characterize its intrinsic uncertainties by comparing the results to photoionization models. We then apply our method to a sample of nearby galaxies using new observations obtained with SOFIA/FIFI-LS in combination with available Herschel/PACS data, and the results are compared with optical N/O estimates. We find evidence for a systematic offset between the far-IR and optically derived N/O. We argue that the likely reason is that our far-IR method is biased toward younger and denser H ii regions, while the optical methods are biased toward older H ii regions as well as diffuse ionized gas. This work provides a local template for studies of the abundance of interstellar medium in the early Universe.

Purpose While the use of long-endurance remotely piloted aircraft systems (LE-RPAS) is frequently associated with military operations, their core capabilities of long-range, low-cost and high-quality optics and communications systems have considerable potential benefit in supporting the work of humanitarian logisticians. The purpose of this paper is, therefore, to demonstrate how LE-RPAS could be used to improve the logistic response to a rapid onset disaster. Design/methodology/approach Using the response to the Cyclone Pam that struck Vanuatu in March 2015 as an example, this paper provides an overview of how LE-RPAS could be used to support the post-disaster needs assessment and subsequent response processes. In addition, it provides a high-level route map to develop the people, process and technology requirements that would support the operational deployment of the LE-RPAS capabilities. Findings On the basis of the analysis of the published literature and the resultant assessment of the benefits of LE-RPAS to support humanitarian logistic (HL) operations, it is concluded that a formal “proof of concept” trial should be undertaken, and the results be made available to the humanitarian community. Research limitations/implications This paper is conceptual in nature, but has been developed through an analysis of the literature relating to remotely piloted aircraft systems (RPAS) and HLs. A route map through which the paper’s conclusions can be validated is also offered. Practical implications LE-RPAS have great potential to provide a swifter understanding of the impact of a disaster, particularly those where the location is remote from the main centres of population. This would allow the affected country’s National Disaster Management Organisation, together with those of supporting countries, to react more efficiently and effectively. In particular, it would allow a swifter transition from a “guess-based” push approach to one that more accurately reflects the disaster’s impact – i.e. a pull-based logistic response. Social implications Given the military genesis of RPAS, it will be important to ensure that those engaged in their operation are sensitive to the implications of this. In particular, it will be essential to ensure that any humanitarian operations involving RPAS are undertaken in an ethical way that respects, for example, the privacy and safety of the affected population. Originality/value While there is some emerging discussion on the humanitarian-related use of RPAS in the literature, this generally reflects the operation of small aircraft with limited range and payload capabilities. Useful though such RPAS unquestionably are, this paper expands the discussion of how such systems can support the humanitarian logistician by considering the benefits and challenges of operating long-endurance aircraft.

We present results from deep H i and optical imaging of AGC 229101, an unusual H i source detected at v helio =7116 km s−1 in the Arecibo Legacy Fast ALFA (ALFALFA) blind H i survey. Initially classified as a candidate “dark” source because it lacks a clear optical counterpart in Sloan Digital Sky Survey (SDSS) or Digitized Sky Survey 2 (DSS2) imaging, AGC 229101 has 109.31±0.05 M ⊙ of H i, but an H i line width of only 43 ± 9 km s−1. Low-resolution Westerbork Synthesis Radio Telescope (WSRT) imaging and higher-resolution Very Large Array (VLA) B-array imaging show that the source is significantly elongated, stretching over a projected length of ∼80 kpc. The H i imaging resolves the source into two parts of roughly equal mass. WIYN partially populated One Degree Imager (pODI) optical imaging reveals a faint, blue optical counterpart coincident with the northern portion of the H i. The peak surface brightness of the optical source is only μ g ∼ 26.6 mag arcsec−2, well below the typical cutoff that defines the isophotal edge of a galaxy, and its estimated stellar mass is only 107.32±0.33 M ⊙, yielding an overall neutral gas-to-stellar mass ratio of M/M * = 98 − 52 + 111 . We demonstrate the extreme nature of this object by comparing its properties with those of other H i-rich sources in ALFALFA and the literature. We also explore potential scenarios that might explain the existence of AGC 229101, including a tidal encounter with neighboring objects and a merger of two dark H i clouds.