NGC 4705 — a tilted SAB(s)bc spiral in Virgo, its split bulge and knotty inner ring laid bare against a deep field of resolved background galaxies
NGC 4705 is a SAB(s)bc spiral galaxy in the constellation Virgo, catalogued as PGC 43350 and MCG -01-33-016, with the RC3 noting its high inclination and spindle-like appearance
At a NED mean redshift-independent distance of ~152 million light-years and a Hubble-flow CMB distance of ~223 million light-years — the 32 percent disagreement reflects significant peculiar motion in the Virgo infall region — with an RC3 D_25 angular diameter of 3.02 arcminutes and apparent magnitude V 12.6, the galaxy spans roughly 134,000 light-years across using the redshift-independent value, comparable to the Milky Way
Tilted close to edge-on, NGC 4705 presents a luminous yellow bulge bisected by a prominent dark dust lane that cuts in front of the central region from the near side of the inclined disk, producing the characteristic split-bulge appearance of high-inclination intermediate spirals where the upper bulge peeks through above the obscuring band
Tightly wound spiral arms wrap the inner disk and reveal a knotty pseudo-ring of bright blue OB associations and pink HII complexes traced as a chain of resolved clumps along the near-side arm just above the central dust lane, while the southwestern arm extends asymmetrically well beyond the opposite side and fades into a faint stream of material — an asymmetry already flagged in the APM survey, which placed the optical centroid offset toward the southeastern part of the galaxy
The SAB(s) classification indicates a weak central bar transitioning smoothly into the spiral pattern without an inner ring, though at this inclination the bar is photometrically hidden behind the bulge and only the kinematic signature would betray it
The deep background swarms with resolved galaxies of every morphology — a small edge-on spiral sits just south of NGC 4705, an elongated background system anchors the upper-left field, and a tight grouping at the far upper-left edge resembles a distant compact group — an unusually clean view through galactic latitude +57.7° where foreground Milky Way extinction drops to A_V 0.08 magnitudes, with a faint trace of integrated flux nebula visible in the upper-left as the only foreground veil
This is the kind of inclined SAB(s)bc spiral where the geometry of the disk teaches the structure — split bulge, threaded dust, knotty pseudo-ring, asymmetric outer arms and diffuse halo all separating cleanly along the line of sight, with the high galactic latitude turning the foreground into a deep-field laboratory for the galaxies beyond
Imaged in LRGB on the ASA Astrosysteme AZ 1500, Camera Moravian C5A 150M, at Observatorio El Sauce, Chile
Image Acquisition and Processing: Mike Selby