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UGC 4277 Distant Galaxy Group, Lynx, ANNOTATED
UGC 4277 Distant Galaxy Group, Lynx
UGC4277 is a giant edge-on spiral galaxy, morphological type SC, which is gravitationally bound to, but not tidally interacting with, two smaller galaxies, MCG+09-14-017 and MCG+09-14-012. Since they have similar redshifts and distances, their relative sizes and separation on the image are essentially to scale. From the measurable properties (redshift, apparent magnitude, and angular size), we can derive UGC4277 light travel distance (lookback time) of 250 Mly, redshift recession velocity of 5,407 km/s, and actual diameter of 284,000 ly. This is about 30% larger than the Andromeda Galaxy, and nearly twice the size of the Milky Way. Due to its edge-on orientation, its integrated apparent magnitude and the calculated absolute magnitude are significantly underestimated for two reasons. First, it presents to the observer a much smaller surface area than a face-on galaxy. And second, much of its starlight is absorbed and scattered by thick layers of gas and dust in its galactic plane. Prominent dark dust lanes are easily visible even at the low resolution and small scale of the attached image. UGC4277 has an active galactic nucleus (AGN), which indicates the presence of an accreting central supermassive black hole (SMBH.
Edge-on galaxies are of great interest in the study of galactic evolution because the dynamic distribution of stars, dust, and atomic gas can be analyzed both along the galactic plane and perpendicularly to it. Radio frequency studies of UGC4277 by Allaert et al. (2015) revealed the presence of a primordial atomic hydrogen envelope, three times thicker than the visible disk. As this gas gravitates toward the galactic plane, it condenses into clouds of molecular gas, which eventually collapse to form a "rain" of low metallicity stars. Metals (in astronomy all elements heavier that helium) are produced by stellar nucleosynthesis, and are dispersed into the interstellar medium (ISM) by stellar winds, supernova explosions, and neutron star collisions. Through various processes, a fraction of metals condenses into small dust grains which on average constitute about 0.1% of the galactic baryonic mass. While most of the dust resides in the galactic plane, a part of it can be detected in the form of a "dust-scattered ultraviolet halo" around the galaxy. This "extraplanar" dust appears to be defying gravity, probably suspended by radiation pressure and the plumes of hot gases arising from the galactic disk and bulge. Assuming similar total dust mass fraction, it is expected that starburst galaxies with numerous hot, blue stars and more intense ultraviolet radiation would manifest more prominent extraplanar dust halos. Jong-Ho Shinn (2018), who compared visible band to GALEX ultraviolet images of 23 edge-on galaxies reported, among other findings, a moderate to low extraplanar dust halo around UGC4277, implying a similarly moderate to low star formation rate.
The other two galaxies in the group are MCG+09-14-017 and MCG+09-14-012. The former is oriented face-on, and has a LINER type active galactic nucleus. It is approximately half the diameter and half the brightness of the Milky Way. Both appear to be barred spirals with slightly deformed spiral arms probably due to mild tidal interaction in the remote past. A number of small, background galaxies, listed in the chart on the annotated image, lie at distances between 540 and 1,610 million light years. Four bright quasars are also identified. The most remote of these is SDSS J081428.78+524045.2, located at a light travel distance (lookback time) of 10.4 billion light years. In the present cosmological epoch, its proper (comoving) distance is 17 Bly, and proper recesion velocity 367,941 km/s. Since its recession velocity is presently superluminal, the quasar lies beyond the cosmic event horizon, and the light it is presently emitting can never reach us.
Image details:
-Remote Takahashi TOA 150 x 1105 mm, Paramount GT GEM
-OSC 35 x 300 sec, 2x drizzle, 50% linear crop
-Software: DSS, XnView, Starnet++ v2, StarTools v1.3 and 1.7, Cosmological Calculator v3
UGC 4277 Distant Galaxy Group, Lynx, ANNOTATED
UGC 4277 Distant Galaxy Group, Lynx
UGC4277 is a giant edge-on spiral galaxy, morphological type SC, which is gravitationally bound to, but not tidally interacting with, two smaller galaxies, MCG+09-14-017 and MCG+09-14-012. Since they have similar redshifts and distances, their relative sizes and separation on the image are essentially to scale. From the measurable properties (redshift, apparent magnitude, and angular size), we can derive UGC4277 light travel distance (lookback time) of 250 Mly, redshift recession velocity of 5,407 km/s, and actual diameter of 284,000 ly. This is about 30% larger than the Andromeda Galaxy, and nearly twice the size of the Milky Way. Due to its edge-on orientation, its integrated apparent magnitude and the calculated absolute magnitude are significantly underestimated for two reasons. First, it presents to the observer a much smaller surface area than a face-on galaxy. And second, much of its starlight is absorbed and scattered by thick layers of gas and dust in its galactic plane. Prominent dark dust lanes are easily visible even at the low resolution and small scale of the attached image. UGC4277 has an active galactic nucleus (AGN), which indicates the presence of an accreting central supermassive black hole (SMBH.
Edge-on galaxies are of great interest in the study of galactic evolution because the dynamic distribution of stars, dust, and atomic gas can be analyzed both along the galactic plane and perpendicularly to it. Radio frequency studies of UGC4277 by Allaert et al. (2015) revealed the presence of a primordial atomic hydrogen envelope, three times thicker than the visible disk. As this gas gravitates toward the galactic plane, it condenses into clouds of molecular gas, which eventually collapse to form a "rain" of low metallicity stars. Metals (in astronomy all elements heavier that helium) are produced by stellar nucleosynthesis, and are dispersed into the interstellar medium (ISM) by stellar winds, supernova explosions, and neutron star collisions. Through various processes, a fraction of metals condenses into small dust grains which on average constitute about 0.1% of the galactic baryonic mass. While most of the dust resides in the galactic plane, a part of it can be detected in the form of a "dust-scattered ultraviolet halo" around the galaxy. This "extraplanar" dust appears to be defying gravity, probably suspended by radiation pressure and the plumes of hot gases arising from the galactic disk and bulge. Assuming similar total dust mass fraction, it is expected that starburst galaxies with numerous hot, blue stars and more intense ultraviolet radiation would manifest more prominent extraplanar dust halos. Jong-Ho Shinn (2018), who compared visible band to GALEX ultraviolet images of 23 edge-on galaxies reported, among other findings, a moderate to low extraplanar dust halo around UGC4277, implying a similarly moderate to low star formation rate.
The other two galaxies in the group are MCG+09-14-017 and MCG+09-14-012. The former is oriented face-on, and has a LINER type active galactic nucleus. It is approximately half the diameter and half the brightness of the Milky Way. Both appear to be barred spirals with slightly deformed spiral arms probably due to mild tidal interaction in the remote past. A number of small, background galaxies, listed in the chart on the annotated image, lie at distances between 540 and 1,610 million light years. Four bright quasars are also identified. The most remote of these is SDSS J081428.78+524045.2, located at a light travel distance (lookback time) of 10.4 billion light years. In the present cosmological epoch, its proper (comoving) distance is 17 Bly, and proper recesion velocity 367,941 km/s. Since its recession velocity is presently superluminal, the quasar lies beyond the cosmic event horizon, and the light it is presently emitting can never reach us.
Image details:
-Remote Takahashi TOA 150 x 1105 mm, Paramount GT GEM
-OSC 35 x 300 sec, 2x drizzle, 50% linear crop
-Software: DSS, XnView, Starnet++ v2, StarTools v1.3 and 1.7, Cosmological Calculator v3