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NGC 2146 Camelopardalis, A Peculiar Spiral Galaxy, and A Possible Blue Compact Dwarf
NGC 2146 is a disrupted barred spiral galaxy in the constellation of Camelopardalis. It was discovered in 1876 by German astronomer Friedrich Winnecke, who was known for his work on comets, asteroids, and double stars. The galaxy is classified as SB(s)ab pec, indicating a barred spiral galaxy with tightly wound arms, and no ring around the central bulge. The "pec" descriptor refers to the "peculiar" appearance of the spiral arms, one of which is markedly stretched and inclined to the galactic plane by nearly 45*. Very high star formation rate (SFR) and densities within both spiral arms resembling large stellar trails suggest the galaxy recently merged with one or two substantial dwarf satellites, and is presently reforming into a larger object. Some sources suggest that NGC 2146 may have interacted with a nearby small galaxy, NGC 2146a, however that seems unlikely because the small galaxy's spiral structure appears quite well preserved. Aside from its disrupted aspect and starburst activity, NGC 2146 is also distinctive due to its conspicuous dust lanes extending across the background glow of the galactic core. Spectroscopy of the central region reveals widening of spectral lines. This indicates a high velocity dispersion of the stars in the nucleus due to the presence of a central supermassive black hole (SMBH). Absence of an active galactic nucleus means thet the central SMBH is not presently accreting matter.
Assuming its measured redshift of 0.00298 is caused exclusively by the expansion of space (Hubble Flow), NGC 2146 would lie at a distance of 41.3 Mly. However, the median value of 16 redshift-independent distance measurements is 17.40 Mpc, or 56.72 Mly. The two distance estimates differ because the measured redshift actually results from the combined motion due to Hubble Flow and the object's "peculiar velocity" through space. When available in a statistically valid number of measurements, redshift-independent estimates are generally regarded as more accurate for nearby galaxies, closer than approximately 140 Mly. From the apparent magnitude and angular size, accepting the distance of 56.72 Mly, we can derive the galaxy's actual diameter of 97,000 ly and absolute magnitude of -20.64. NGC 2146 is some 20-30% smaller, and about 15% less bright than the Milky Way.
Chandra CXC HIPS X-ray sky survey (SIMBAD) shows numerous X-ray sources within the NGC 2146 core, in the spiral arms, and in its halo. While it is possible that some of the sources may be local to the Milky Way, clustering of the sources around NGC 2146 suggests that most are of extragalactic origin.
The most common mechanism for X-ray emission in astronomical objects involves very hot ionized gases at temperatures of millions to hundreds of millions Kelvin (K). Stellar coronas, especially in young blue giants, emit X-rays, though they are regarded as relatively weak sources. Stronger emissions come from "X-ray binaries", "cataclysmic variable stars", supernova remnants, and hot gas clouds around stellar nurseries. Still stronger localized X-ray emissions are "ultra-luminous X-ray sources" or ULX. These are produced by actively accreting intermediate mass black holes (IMBH), usually identified in galactic disks, and by central supermassive black holes (SMBH) which define "active galactic nuclei" (AGN). By far the most powerful, but very diffuse, sources of X-rays are galaxy clusters.
While it is logical to expect numerous X-ray emissions in an actively merging starburst galaxy with accelerated stellar evolution, NGC 2146 has no identified ultra-luminous X-ray sources and no active galactic nucleus. This does not imply the galaxy contains no intermediate or supermassive black holes, but merely that they are not actively accreting.
On closer inspection, the attached image records a number of small, faint background galaxies, but only two of these have identifiers associated with measurable data. Based on a subjective estimate of their angular size and apparent brightness, the rest probably lie at approximate distances between 1 and 2 Bly. The image also records a single quasar (QSO) at a light travel distance (lookback time) of 9.2 Bly.
The distinctly blue galaxy Gaia DR3 1140883127890416128 may belong to a class of special objects: "Blue Compact Dwarf" galaxies (BCDs), which are field dwarf galaxies with inexplicably high star formation rates. BCDs are rare local versions of the "Faint Blue Galaxies" (FBGs), the most common galaxy type at redshifts between 0.1 and 2, but which are undetectable with small instruments. I estimate the apparent magnitude of this object around 20.5 and angular size at 0.15 arcmin. Unfortunately, no redshift information or color photometry is available in extragalactic databases, and the suspected nature of this galaxy can not be confirmed. For additional details on BCDs and FBGs please see section 32, Dwarf Galaxies, subsections 6 and 7 here:
www.cloudynights.com/articles/cat/articles/basic-extragal...
Image Details:
Remote Takahashi TOA 150x1105 mm
OSC 31x300 sec, 2x drizzle, 40% linear crop, 26x17'
Software:
DSS, XnView, StarNet++ v2, StarTools v1.8
Extragalactic Cosmological Calculator v2
www.cloudynights.com/gallery/image/123530-extragalactic-c...
NGC 2146 Camelopardalis, A Peculiar Spiral Galaxy, and A Possible Blue Compact Dwarf
NGC 2146 is a disrupted barred spiral galaxy in the constellation of Camelopardalis. It was discovered in 1876 by German astronomer Friedrich Winnecke, who was known for his work on comets, asteroids, and double stars. The galaxy is classified as SB(s)ab pec, indicating a barred spiral galaxy with tightly wound arms, and no ring around the central bulge. The "pec" descriptor refers to the "peculiar" appearance of the spiral arms, one of which is markedly stretched and inclined to the galactic plane by nearly 45*. Very high star formation rate (SFR) and densities within both spiral arms resembling large stellar trails suggest the galaxy recently merged with one or two substantial dwarf satellites, and is presently reforming into a larger object. Some sources suggest that NGC 2146 may have interacted with a nearby small galaxy, NGC 2146a, however that seems unlikely because the small galaxy's spiral structure appears quite well preserved. Aside from its disrupted aspect and starburst activity, NGC 2146 is also distinctive due to its conspicuous dust lanes extending across the background glow of the galactic core. Spectroscopy of the central region reveals widening of spectral lines. This indicates a high velocity dispersion of the stars in the nucleus due to the presence of a central supermassive black hole (SMBH). Absence of an active galactic nucleus means thet the central SMBH is not presently accreting matter.
Assuming its measured redshift of 0.00298 is caused exclusively by the expansion of space (Hubble Flow), NGC 2146 would lie at a distance of 41.3 Mly. However, the median value of 16 redshift-independent distance measurements is 17.40 Mpc, or 56.72 Mly. The two distance estimates differ because the measured redshift actually results from the combined motion due to Hubble Flow and the object's "peculiar velocity" through space. When available in a statistically valid number of measurements, redshift-independent estimates are generally regarded as more accurate for nearby galaxies, closer than approximately 140 Mly. From the apparent magnitude and angular size, accepting the distance of 56.72 Mly, we can derive the galaxy's actual diameter of 97,000 ly and absolute magnitude of -20.64. NGC 2146 is some 20-30% smaller, and about 15% less bright than the Milky Way.
Chandra CXC HIPS X-ray sky survey (SIMBAD) shows numerous X-ray sources within the NGC 2146 core, in the spiral arms, and in its halo. While it is possible that some of the sources may be local to the Milky Way, clustering of the sources around NGC 2146 suggests that most are of extragalactic origin.
The most common mechanism for X-ray emission in astronomical objects involves very hot ionized gases at temperatures of millions to hundreds of millions Kelvin (K). Stellar coronas, especially in young blue giants, emit X-rays, though they are regarded as relatively weak sources. Stronger emissions come from "X-ray binaries", "cataclysmic variable stars", supernova remnants, and hot gas clouds around stellar nurseries. Still stronger localized X-ray emissions are "ultra-luminous X-ray sources" or ULX. These are produced by actively accreting intermediate mass black holes (IMBH), usually identified in galactic disks, and by central supermassive black holes (SMBH) which define "active galactic nuclei" (AGN). By far the most powerful, but very diffuse, sources of X-rays are galaxy clusters.
While it is logical to expect numerous X-ray emissions in an actively merging starburst galaxy with accelerated stellar evolution, NGC 2146 has no identified ultra-luminous X-ray sources and no active galactic nucleus. This does not imply the galaxy contains no intermediate or supermassive black holes, but merely that they are not actively accreting.
On closer inspection, the attached image records a number of small, faint background galaxies, but only two of these have identifiers associated with measurable data. Based on a subjective estimate of their angular size and apparent brightness, the rest probably lie at approximate distances between 1 and 2 Bly. The image also records a single quasar (QSO) at a light travel distance (lookback time) of 9.2 Bly.
The distinctly blue galaxy Gaia DR3 1140883127890416128 may belong to a class of special objects: "Blue Compact Dwarf" galaxies (BCDs), which are field dwarf galaxies with inexplicably high star formation rates. BCDs are rare local versions of the "Faint Blue Galaxies" (FBGs), the most common galaxy type at redshifts between 0.1 and 2, but which are undetectable with small instruments. I estimate the apparent magnitude of this object around 20.5 and angular size at 0.15 arcmin. Unfortunately, no redshift information or color photometry is available in extragalactic databases, and the suspected nature of this galaxy can not be confirmed. For additional details on BCDs and FBGs please see section 32, Dwarf Galaxies, subsections 6 and 7 here:
www.cloudynights.com/articles/cat/articles/basic-extragal...
Image Details:
Remote Takahashi TOA 150x1105 mm
OSC 31x300 sec, 2x drizzle, 40% linear crop, 26x17'
Software:
DSS, XnView, StarNet++ v2, StarTools v1.8
Extragalactic Cosmological Calculator v2
www.cloudynights.com/gallery/image/123530-extragalactic-c...