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NGC 4725 Coma Berenices, A One-Armed Spiral Galaxy and 7 Quasars, ANNOTATED
NGC 4725 Coma Berenices, A One-Armed Spiral Galaxy and 7 Quasars
NGC 4725 is a large intermediate spiral galaxy in the constellation of Coma Berenices, first documented by W. Herschel in 1785. It is the brightest, but relatively isolated, member of the Coma I Galaxy Group, that is itself a part of the Virgo Galaxy Supercluster which includes our own Milky Way.
Its morphological classification is SAB (r)ab pec, indicating a weakly barred, tightly wound spiral galaxy with a complete ring. The galaxy was assigned the "peculiar" descriptor for several reasons. The ring structure is not concentric with the galactic nucleus, and displays elliptical motion. Unlike most spiral galaxies, NGC 4725 displays only a single spiral arm. And, its galactic disk is warped relative to the galactic plane. These anomalies are almost certainly due to strong gravitational interaction with the neighboring NGC 4747 (ARP 159), which is even more highly deformed. Further evidence of interaction, and probable mergers with smaller satellites, comes from the densities in the faint outer parts of the galactic disk suggestive of "stellar streams". These are marked with "S" on the annotated image. Bright blue OB Associations within the ring and along the spiral arm indicate a high star formation rate (SFR), also triggered by tidal interaction. The reddish color along the inner NE edge of the ring is due to Ha fluorescence of hydrogen clouds partially ionized by the ultraviolet radiation emanating from the swarm of very hot and massive young stars. These "stellar nurseries" are especially prominent on infrared images taken by the Spitzer Space Telescope. Spectroscopic studies of the central region indicate the presence of an active galactic nucleus (AGN) of the Seyfert 2 type, caused by a central suppermassive black hole. SIMBAD extragalactic database lists several radio sources without optical counterparts that may be due to compact clouds of neutal hydrogen. It also lists two ultra-luminous X-ray sources (ULX) which are thought to be associated with moderately accreting intermediate-mass black holes (IMBH).
Based on measurable data, NGC 4725 lies at a light travel distance (lookback time) of 41.1 Mly. This is based on the median value of 48 redshift-independent distance estimates which span an unusually wide range of nearly 3. From the distance, angular size, and apparent magnitude we can derive the actual diameter of 114,000 ly and an absolute magnitude of -21.06, approximately 1.25 times brighter than the Milky Way. From the redshift, which is due to the expansion of space and the galaxy's "peculiar velocity" through space, we calculate a recession velocity of 1,209 km/s. (See the note at the bottom of the chart).
The other prominent object in the field is NGC 4712, an emission line barred spiral galaxy with a curiously attenuated central region, possibly obscured by dust and gas. It lies in the faraway background at a distance of 203 Mly, and is about 122,000 ly in diameter - approximately the size of the Milky Way, but only half as bright.
The field is strewn with numerous remote galaxies, most of which have no identifier or observation data listed. A number of these peer through the translucent envelope of NGC 4725, and are marked with letter "G" on the annotated image.
The field also includes seven very distant quasars (QSOs) listed in the attached chart. At this time, some are substantially brighter and some fainter than their photometric data indicate. Letter "X" on the annotated image indicates the locations of two fairly bright quasars which have apparently faded beyond the limiting magnitude of approximately 20.5. The last six quasars on the list have superluminal "proper recession velocities" in the present epoch. They have receded beyond the "cosmic event horizon", and the light they are now emitting can never reach us. The last two on the list are "hyperluminous quasars", more than 2,000 times brighter than the entire Milky Way galaxy. SDSS J125125.57+252026.2 is the most distant. The photons we are presently recording have travelled 11.7 billion years (lookback = light travel time). In the present epoch, its "comoving = proper distance" is nearly 22 Bly. Over the next few billion years, its redshift will gradually increase until the quasar becomes forever invisible. From the photons' perspective, travelling at the speed of light time does not pass, and their journey was instantaneous.
See the link for more information on ULX, IMBH and quasars:
www.cloudynights.com/articles/cat/articles/basic-extragal...
-Remote Takahashi TOA 150 x 1105mm
-OSC 36 x 300 sec, 2x drizzle, 50% linear crop
-Software:
DSS, XnView, StarNet++ v2, StarTools
Extragalactic Cosmological Calculator v2
www.cloudynights.com/gallery/image/123530-extragalactic-c...
NGC 4725 Coma Berenices, A One-Armed Spiral Galaxy and 7 Quasars, ANNOTATED
NGC 4725 Coma Berenices, A One-Armed Spiral Galaxy and 7 Quasars
NGC 4725 is a large intermediate spiral galaxy in the constellation of Coma Berenices, first documented by W. Herschel in 1785. It is the brightest, but relatively isolated, member of the Coma I Galaxy Group, that is itself a part of the Virgo Galaxy Supercluster which includes our own Milky Way.
Its morphological classification is SAB (r)ab pec, indicating a weakly barred, tightly wound spiral galaxy with a complete ring. The galaxy was assigned the "peculiar" descriptor for several reasons. The ring structure is not concentric with the galactic nucleus, and displays elliptical motion. Unlike most spiral galaxies, NGC 4725 displays only a single spiral arm. And, its galactic disk is warped relative to the galactic plane. These anomalies are almost certainly due to strong gravitational interaction with the neighboring NGC 4747 (ARP 159), which is even more highly deformed. Further evidence of interaction, and probable mergers with smaller satellites, comes from the densities in the faint outer parts of the galactic disk suggestive of "stellar streams". These are marked with "S" on the annotated image. Bright blue OB Associations within the ring and along the spiral arm indicate a high star formation rate (SFR), also triggered by tidal interaction. The reddish color along the inner NE edge of the ring is due to Ha fluorescence of hydrogen clouds partially ionized by the ultraviolet radiation emanating from the swarm of very hot and massive young stars. These "stellar nurseries" are especially prominent on infrared images taken by the Spitzer Space Telescope. Spectroscopic studies of the central region indicate the presence of an active galactic nucleus (AGN) of the Seyfert 2 type, caused by a central suppermassive black hole. SIMBAD extragalactic database lists several radio sources without optical counterparts that may be due to compact clouds of neutal hydrogen. It also lists two ultra-luminous X-ray sources (ULX) which are thought to be associated with moderately accreting intermediate-mass black holes (IMBH).
Based on measurable data, NGC 4725 lies at a light travel distance (lookback time) of 41.1 Mly. This is based on the median value of 48 redshift-independent distance estimates which span an unusually wide range of nearly 3. From the distance, angular size, and apparent magnitude we can derive the actual diameter of 114,000 ly and an absolute magnitude of -21.06, approximately 1.25 times brighter than the Milky Way. From the redshift, which is due to the expansion of space and the galaxy's "peculiar velocity" through space, we calculate a recession velocity of 1,209 km/s. (See the note at the bottom of the chart).
The other prominent object in the field is NGC 4712, an emission line barred spiral galaxy with a curiously attenuated central region, possibly obscured by dust and gas. It lies in the faraway background at a distance of 203 Mly, and is about 122,000 ly in diameter - approximately the size of the Milky Way, but only half as bright.
The field is strewn with numerous remote galaxies, most of which have no identifier or observation data listed. A number of these peer through the translucent envelope of NGC 4725, and are marked with letter "G" on the annotated image.
The field also includes seven very distant quasars (QSOs) listed in the attached chart. At this time, some are substantially brighter and some fainter than their photometric data indicate. Letter "X" on the annotated image indicates the locations of two fairly bright quasars which have apparently faded beyond the limiting magnitude of approximately 20.5. The last six quasars on the list have superluminal "proper recession velocities" in the present epoch. They have receded beyond the "cosmic event horizon", and the light they are now emitting can never reach us. The last two on the list are "hyperluminous quasars", more than 2,000 times brighter than the entire Milky Way galaxy. SDSS J125125.57+252026.2 is the most distant. The photons we are presently recording have travelled 11.7 billion years (lookback = light travel time). In the present epoch, its "comoving = proper distance" is nearly 22 Bly. Over the next few billion years, its redshift will gradually increase until the quasar becomes forever invisible. From the photons' perspective, travelling at the speed of light time does not pass, and their journey was instantaneous.
See the link for more information on ULX, IMBH and quasars:
www.cloudynights.com/articles/cat/articles/basic-extragal...
-Remote Takahashi TOA 150 x 1105mm
-OSC 36 x 300 sec, 2x drizzle, 50% linear crop
-Software:
DSS, XnView, StarNet++ v2, StarTools
Extragalactic Cosmological Calculator v2
www.cloudynights.com/gallery/image/123530-extragalactic-c...