rudykokich
M100 (NGC 4321), NGC 4322, NGC 4328 Interacting Galaxy Group, Coma Berenices
M100 (NGC 4321), NGC 4322, NGC 4328 Interacting Galaxy Group, Coma Berenices
This galaxy was discovered by Pierre Mechain in 1781, then confirmed by Messier 29 days later, and listed as entry 100 in his catalog of nebulae and star clusters. He described the object as a faint nebula without a star. It was later documented by William Herschel who noted a brighter center presumably composed of stars, and by his son John Herschel in 1833 who initially found it to be not very remarkable. Observational notes of the nebula became more interesting as telescope technologies improved over the years. By 1850, M100 appears on the list of 16 "spiral nebulae" identified with Lord Rosse's giant reflector. And by 1888, entry 4321 in Dreyer's New General Catalogue describes the nebula as a "very remarkable... 2-branched spiral... with a bright mottled nucleus." In 1990, M100 was the very first object photographed by the Hubble Space Telescope, revealing a serious spherical aberration flaw in its mirror.
In most amateur telescopes this galaxy remains a humble visual target. However, with even modest apertures, it presents a captivating photographic subject surrounded by a cluster of dwarf companions. M 100 is a nearly face-on grand design spiral galaxy with two well defined spiral arms. Infrared studies of the central region reveal a delicate bar structure, which classifies it as an intermediate spiral of the SAB morphological type. Together with all the galaxies marked in white or blue on the annotated image, M100 is a rapidly moving member of the large Virgo Galaxy Cluster. Since this group has high peculiar velocity, or rapid movement through space relative to the Milky Way, redshifts of these galaxies do not accurately reflect Hubble Flow, or the expansion of space itself, and should not be used to estimate galaxy distances. In the chart below, physical properties of the group are calculated from the redshift-independent distance measurements listed in the NASA Extragalactic Database (NED). Based on the specified median distance of 51.67 million ly, we can calculate M100's diameter of 131,000 ly, and an absolute magnitude (V) of -21.65. In terms of morphology, dimensions, and mass (approximately 400 billion stars), the galaxy is quite similar to the Milky Way. Its greater overall brightness may be due to an active galactic nucleus (AGN) of the Hii LINER type, caused by ionizing radiation emanating from the accretion disk of a central supermassive black hole (SMBH) and/or from central regions of starburst activity.
Even at low resolution, the galaxy reveals many features typical of grand design spirals. Blue floccules in the spiral arms are OB Associations - immense clusters of recently formed large, hot stars. These are typically surrounded by parent clouds of hydrogen gas, which can glow red where they re-emit energy absorbed from starlight. Yellowish color toward the middle is due to a multitude of smaller, ancient stars remaining from the early stages of galaxy formation. Dark stripes and bands weaving through the galaxy disk are large clouds of obscuring dust and gas. And, the bright region in the center is generated by a dense population of ancient stars and by emissions from a central supermassive black hole (SMBH). In some galaxies, M100 included, this nuclear region is surrounded with a ring of rapid new star formation probably driven by nuclear outflows caused by SMBH radiation pressure, SMBH winds and jets, convection plumes, and increased supernova activity.
While it displays localized areas of starburst activity around the nucleus and within spiral arms, like most other spiral galaxies in the Virgo Cluster M100 has a low neutral hydrogen content and a lower average star formation rate (SFR) than what is found in isolated, field galaxies. Hydrogen gas is lost by a process called ram-pressure stripping as a cluster galaxy with high peculiar velocity moves through a relatively dense intergalactic medium (IGM) within a cluster. For more details, see section 41 here:
www.cloudynights.com/articles/cat/articles/basic-extragal...
The attached image demonstrates a number of smaller galaxies, annotated in blue, surrounding M100. Angular proximity and similar redshift values imply - but do not prove - physical proximity and gravitational connection in 3 dimensional space. Unfortunately, redshift-independent distance estimates for five of these galaxies are not available in the literature. In order to guesstimate their physical properties, in the attached chart we make a "reasonable" assumption that their distances are approximately 52 Mly, similar to the fairly well determined M100 distance. Recent studies regarding matter distribution in our local universe reveal that most major galaxies, the Milky Way and the Andromeda included, are surrounded by substantial numbers of irregular, spheroidal, and elliptical dwarf galaxies, and that most of these are passersby rather than satellites. While complex kinematic studies are required to determine which of the galaxies in the image are gravitationally bound, streams of luminous debris between M100, NGC4322, and NGC4328 are conclusive indicators of tidal interaction. Based on their redshifts, NGC4328 had a close encounter with M100 while moving toward its foreground, and NGC4322 while moving toward its background.
The other prominent galaxy in the field is NGC4312, a nearly edge-on unbarred spiral, discovered by W. Herschel in 1787. Based on its median redshift-independent distance estimate of 35.534 Mly and angular size of 4.37 arcmin, this galaxy is about one third the diameter of the Milky Way, and about one ninth as bright. It is another high peculiar velocity member of the Virgo Galaxy Cluster which has lost much of its neutral hydrogen through ram-pressure stripping. Based on X-ray images, the galaxy is suspected of hosting an intermediate mass black hole (IMBH) with a mass between 10,000 and 300,000 solar.
The image also reveals three faint galaxies in the remote background, and a modest quasar (QSO) lying at a distance of 3.56 billion ly.
Image Details:
Remote Takahashi TOA 150 x 1105 mm
OSC 27 x 300 sec exposures, 9 discarded
2x drizzle, 55% linear crop
Software: DSS, StarNet++ v2, XnView, StarTools
M100 (NGC 4321), NGC 4322, NGC 4328 Interacting Galaxy Group, Coma Berenices
M100 (NGC 4321), NGC 4322, NGC 4328 Interacting Galaxy Group, Coma Berenices
This galaxy was discovered by Pierre Mechain in 1781, then confirmed by Messier 29 days later, and listed as entry 100 in his catalog of nebulae and star clusters. He described the object as a faint nebula without a star. It was later documented by William Herschel who noted a brighter center presumably composed of stars, and by his son John Herschel in 1833 who initially found it to be not very remarkable. Observational notes of the nebula became more interesting as telescope technologies improved over the years. By 1850, M100 appears on the list of 16 "spiral nebulae" identified with Lord Rosse's giant reflector. And by 1888, entry 4321 in Dreyer's New General Catalogue describes the nebula as a "very remarkable... 2-branched spiral... with a bright mottled nucleus." In 1990, M100 was the very first object photographed by the Hubble Space Telescope, revealing a serious spherical aberration flaw in its mirror.
In most amateur telescopes this galaxy remains a humble visual target. However, with even modest apertures, it presents a captivating photographic subject surrounded by a cluster of dwarf companions. M 100 is a nearly face-on grand design spiral galaxy with two well defined spiral arms. Infrared studies of the central region reveal a delicate bar structure, which classifies it as an intermediate spiral of the SAB morphological type. Together with all the galaxies marked in white or blue on the annotated image, M100 is a rapidly moving member of the large Virgo Galaxy Cluster. Since this group has high peculiar velocity, or rapid movement through space relative to the Milky Way, redshifts of these galaxies do not accurately reflect Hubble Flow, or the expansion of space itself, and should not be used to estimate galaxy distances. In the chart below, physical properties of the group are calculated from the redshift-independent distance measurements listed in the NASA Extragalactic Database (NED). Based on the specified median distance of 51.67 million ly, we can calculate M100's diameter of 131,000 ly, and an absolute magnitude (V) of -21.65. In terms of morphology, dimensions, and mass (approximately 400 billion stars), the galaxy is quite similar to the Milky Way. Its greater overall brightness may be due to an active galactic nucleus (AGN) of the Hii LINER type, caused by ionizing radiation emanating from the accretion disk of a central supermassive black hole (SMBH) and/or from central regions of starburst activity.
Even at low resolution, the galaxy reveals many features typical of grand design spirals. Blue floccules in the spiral arms are OB Associations - immense clusters of recently formed large, hot stars. These are typically surrounded by parent clouds of hydrogen gas, which can glow red where they re-emit energy absorbed from starlight. Yellowish color toward the middle is due to a multitude of smaller, ancient stars remaining from the early stages of galaxy formation. Dark stripes and bands weaving through the galaxy disk are large clouds of obscuring dust and gas. And, the bright region in the center is generated by a dense population of ancient stars and by emissions from a central supermassive black hole (SMBH). In some galaxies, M100 included, this nuclear region is surrounded with a ring of rapid new star formation probably driven by nuclear outflows caused by SMBH radiation pressure, SMBH winds and jets, convection plumes, and increased supernova activity.
While it displays localized areas of starburst activity around the nucleus and within spiral arms, like most other spiral galaxies in the Virgo Cluster M100 has a low neutral hydrogen content and a lower average star formation rate (SFR) than what is found in isolated, field galaxies. Hydrogen gas is lost by a process called ram-pressure stripping as a cluster galaxy with high peculiar velocity moves through a relatively dense intergalactic medium (IGM) within a cluster. For more details, see section 41 here:
www.cloudynights.com/articles/cat/articles/basic-extragal...
The attached image demonstrates a number of smaller galaxies, annotated in blue, surrounding M100. Angular proximity and similar redshift values imply - but do not prove - physical proximity and gravitational connection in 3 dimensional space. Unfortunately, redshift-independent distance estimates for five of these galaxies are not available in the literature. In order to guesstimate their physical properties, in the attached chart we make a "reasonable" assumption that their distances are approximately 52 Mly, similar to the fairly well determined M100 distance. Recent studies regarding matter distribution in our local universe reveal that most major galaxies, the Milky Way and the Andromeda included, are surrounded by substantial numbers of irregular, spheroidal, and elliptical dwarf galaxies, and that most of these are passersby rather than satellites. While complex kinematic studies are required to determine which of the galaxies in the image are gravitationally bound, streams of luminous debris between M100, NGC4322, and NGC4328 are conclusive indicators of tidal interaction. Based on their redshifts, NGC4328 had a close encounter with M100 while moving toward its foreground, and NGC4322 while moving toward its background.
The other prominent galaxy in the field is NGC4312, a nearly edge-on unbarred spiral, discovered by W. Herschel in 1787. Based on its median redshift-independent distance estimate of 35.534 Mly and angular size of 4.37 arcmin, this galaxy is about one third the diameter of the Milky Way, and about one ninth as bright. It is another high peculiar velocity member of the Virgo Galaxy Cluster which has lost much of its neutral hydrogen through ram-pressure stripping. Based on X-ray images, the galaxy is suspected of hosting an intermediate mass black hole (IMBH) with a mass between 10,000 and 300,000 solar.
The image also reveals three faint galaxies in the remote background, and a modest quasar (QSO) lying at a distance of 3.56 billion ly.
Image Details:
Remote Takahashi TOA 150 x 1105 mm
OSC 27 x 300 sec exposures, 9 discarded
2x drizzle, 55% linear crop
Software: DSS, StarNet++ v2, XnView, StarTools