With the published data of apparent axis ratios for 1109 ultra-diffuse galaxies (UDGs) located in 17 low-redshift (z ∼ 0.020–0.063) galaxy clusters and 84 UDGs in two intermediate-redshift (z ∼ 0.308–0.348) clusters, we take advantage of a Markov Chain Monte Carlo approach and assume a triaxial model to investigate the intrinsic morphologies of UDGs. In contrast to the conclusion of Burkert, i.e., the underlying shapes of UDGs are purely prolate (C = B < A), we find that the data favor the oblate-triaxial models (i.e., thick disks with ) over the nearly prolate ones. We also find that the intrinsic morphologies of UDGs are related to their stellar masses/luminosities, environments, and redshifts. First, the more luminous UDGs have puffier morphologies compared with the less luminous counterparts; the UDG morphologic dependence on luminosity is distinct from that of the typical quiescent dwarf ellipticals (dEs) and dwarf spheroidals (dSphs); in this sense, UDGs may not be simply treated as an extension of the dE/dSph class with similar evolutionary histories; they may differ not only in size. Second, the UDGs with smaller clustercentric distances are more puffed up, compared with the counterparts with larger clustercentric distances; in combination with the UDG thickness dependence on luminosity, the puffier morphologies of UDGs with high luminosities or located in the denser environments are very likely to be attributed to tidal interactions with massive galaxies. Third, we find that the intermediate-redshift UDGs are more flattened, compared with the low-redshift counterparts, which plausibly suggests a “disky” origin for the high-redshift, newly born UDGs.

We present the results from our Atacama Large Millimeter/submillimeter Array (ALMA) imaging observations of the CO(7−6), [C i] 370 μm (hereafter [C i]), and [N ii] 205 μm (hereafter [N ii]) lines and their underlying continuum emission of BRI 1335-0417, an infrared bright quasar at z = 4.407. At the achieved resolutions of ∼1.″1 to 1.″2 (or 7.5–8.2 kpc), the continuum at 205 and 372 μm (rest frame), the CO(7−6), and the [C i] emissions are at best barely resolved whereas the [N ii] emission is well resolved with a beam-deconvolved major axis of 1.″3(±0.″3) or 9(±2) kpc. As a warm dense gas tracer, the CO(7−6) emission shows a more compact spatial distribution and a significantly higher peak velocity dispersion than the other two lines that probe lower density gas, a picture favoring a merger-triggered star formation (SF) scenario over an orderly rotating SF disk. The CO(7−6) data also indicate a possible QSO-driven gas outflow that reaches a maximum line-of-sight velocity of 500–600 km s⁻¹. The far-infrared (FIR) dust temperature (T _dust ) of 41.5 K from a graybody fit to the continuum agrees well with the average T _dust inferred from various line luminosity ratios. The resulting L _CO(7–6)/L _FIR luminosity ratio is consistent with that of local luminous infrared galaxies powered predominantly by SF. The L _CO(7–6)-inferred SF rate is 5.1(±1.5) × 10³ M _⊙ yr⁻¹. The system has an effective star-forming region of kpc in diameter and a molecular gas reservoir of ∼5 × 10¹¹ M _⊙.

We investigate the on-average properties for 28 star-forming ultra-diffuse galaxies (UDGs) located in low-density environments, by stacking their spectra from the Sloan Digital Sky Survey. These relatively isolated UDGs, with stellar masses of , have the on-average total stellar metallicity [M/H] ∼ −0.82 ± 0.14, iron metallicity [Fe/H] ∼ −1.00 ± 0.16, stellar age t _* ∼ 5.2 ± 0.5 Gyr, α-enhancement [α/Fe] ∼ 0.24 ± 0.10, and oxygen abundance 12+log(O/H) ∼ 8.16 ± 0.06, as well as central stellar velocity dispersion 54 ± 12 km s⁻¹. On the star formation rate versus stellar mass diagram, these UDGs are located lower than the extrapolated star-forming main sequence from the massive spirals, but roughly follow the main sequence of low-surface-brightness dwarf galaxies. We find that these star-forming UDGs are not particularly metal-poor or metal-rich for their stellar masses, as compared with the metallicity–mass relations of the nearby typical dwarfs. With the UDG data of this work and previous studies, we also find a coarse correlation between [Fe/H] and magnesium-element enhancement [Mg/Fe] for UDGs: [Mg/Fe] ≃ −0.43(±0.26) [Fe/H] −0.14(±0.40).

The complete mitochondrial genome of Apatura ilia (GenBank accession no. JF437925) was determined as a circular DNA molecule of 15 242 bp, with common genes of 13 putative proteins, 2 rRNAs, and 22 tRNAs and of the same gene arrangement as in other sequenced lepidopterans. All protein-coding genes had the typical start codon ATN, except for the COI's using CGA as its start codon as previously demonstrated in other lepidopteran species. The comparison of the nucleotide sequences of the A. ilia mitogenome with ten other Nymphalidae species showed nearly identical gene orientation and arrangement, with only a few alterations in non-coding fragments. The nucleotide composition and codon frequency all fell into the range estimated for the order Lepidoptera. The A. ilia mitochondrial genome had the canonical set of 22 tRNA genes folded in the typical cloverleaf structure, with an unique exception of tRNA(Ser) (AGN). The mitochondrial genes from A. ilia were overlapped in a total of 33 bp at 9 locations, as well as interleaved with a total of 155 bp intergenic spacers, spread over 12 regions with the size ranging from 1 to 49 bp. Furthermore, the spacer between ND6 and Cyt b harbored a microsatellite-like repeat (TA)(23) not found in other completely sequenced nymphalid genomes. The 403 bp AT-rich region harbored two conserved motifs (ATAGA, ATTTA), a 21 bp polyT stretch, a 10 bp poly-A region, along with two microsatellite-like repeats ( (TA)(10) and (TA)(7)), as detected in other nymphalid butterflies.

We present the observed Hα flux and derived star formation rates (SFRs) for a fall sample of low-surface-brightness galaxies (LSBGs). The sample is selected from the fall sky region of the 40% ALFALFA H i Survey–SDSS DR7 photometric data, and all the Hα images were obtained using the 2.16 m telescope, operated by the National Astronomy Observatories, Chinese Academy of Sciences. A total of 111 LSBGs were observed and Hα flux was measured in 92 of them. Though almost all the LSBGs in our sample are H i-rich, their SFRs, derived from the extinction and filter-transmission-corrected Hα flux, are less than 1 M _☉ yr⁻¹. LSBGs and star-forming galaxies have similar H i surface densities, but LSBGs have much lower SFRs and SFR surface densities than star-forming galaxies. Our results show that LSBGs deviate from the Kennicutt–Schmidt law significantly, which indicates that they have low star formation efficiency. The SFRs of LSBGs are close to average SFRs in Hubble time and support previous arguments that most of the LSBGs are stable systems and they tend to seldom contain strong interactions or major mergers in their star formation histories.