NGC 4565
Edge-on spiral galaxy with a warped disk and radio halo.
NGC 4565—also called the Needle Galaxy, Flying Saucer Galaxy, Berenice's Hair Clip, or Caldwell 38—is an edge-on spiral galaxy located roughly 30 to 50 million light-years away in the constellation Coma Berenices. It sits near the North Galactic Pole and shines at a visual magnitude of about 10. William Herschel spotted it on April 6, 1785, and it stands out as a classic example of an edge-on spiral, earning its "Needle" nickname from its slender appearance.
This galaxy is a giant, outshining even the Andromeda Galaxy. Its central bulge has sparked debate: without clear data on star motions within it, photometric measurements alone can't settle the matter. However, the bulge's exponential shape hints that NGC 4565 might be a barred spiral. Observations from the Spitzer Space Telescope confirmed a central bar, revealed a pseudobulge inside it, and showed an inner ring.
Deep optical surveys reveal that the galaxy's disk is slightly warped and extended, likely from ongoing interactions with neighboring satellite galaxies or others in the Coma I group. Ultraviolet images from GALEX highlight this warp at the disk's edge more clearly than other surveys. Using the LOw-Frequency ARray (LOFAR), astronomers at the University of Hamburg detected a diffuse radio halo around NGC 4565. They also found a warp in the radio continuum that resembles a neutral hydrogen line warp, along with a slight flaring of the radio halo. This flaring is thought to be caused by the warp, since vertical intensity profiles are asymmetric and match the warp's shape. The warp's minimum age is estimated at about 130 million years—the spectral age of the galaxy's cosmic ray electrons, which are transported into the warp. This suggests NGC 4565 may be recovering from a period of more intense star formation, likely triggered by an interaction with one or both of its satellites. An H I bridge stretching from NGC 4565 to IC 3571 also points to a recent interaction in cosmic terms.
NGC 4565 is grouped with NGC 4562, IC 3543, and IC 3546 as Holm 426, a designation from Erik Holmberg's 1937 study of double and multiple galaxies. It has at least two satellite galaxies—NGC 4562 and IC 3571—one of which is actively interacting with it. The galaxy hosts roughly 240 globular clusters, more than the Milky Way, and ranks among the brightest members of the Coma I Group.
Quick Facts
- Epoch
- J2000
- Ra
- 12 · 36 · 20.7710
- Dec
- +25 · 59 · 15.678
- Z
- 0.004276
- H Radial V
- 1282 ± 1 km/s
- Dist Ly
- 11.700 ± 0.697 Mpc / 53 ± 4 Mly (16.2 ± 1.3 Mpc)
- Appmag V
- 10.42
- Constellation Name
- Coma Berenices
Facts from the source article.
Lore & Background
NGC 4565 is a giant spiral galaxy more luminous than the Andromeda Galaxy. Much speculation exists concerning the nature of its central bulge; photometric data alone cannot adjudge among various options, though its exponential shape suggested it is a barred spiral galaxy. Studies with the Spitzer Space Telescope confirmed the presence of a central bar and also showed a pseudobulge within it, as well as an inner ring.
This edge-on galaxy exhibits a slightly warped and extended disk under deep optical surveys, likely due to ongoing interaction with neighboring satellite galaxies or other galaxies in the Coma I group. GALEX images show the slight warp at the edge of the disc more clearly than other surveys. Using the LOw-Frequency ARray (LOFAR), astronomers discovered a diffuse radio halo around NGC 4565, and a warp was detected in the radio continuum reminiscent of a neutral hydrogen line warp, identifying a slight flaring of the galaxy's radio halo. It is assumed this flaring is caused by the warp, as vertical intensity profiles are asymmetric in agreement with the warp. A minimum age for the warp was estimated at approximately 130 million years, the spectral age of the galaxy's cosmic ray electrons during which they are transported into the warp, indicating NGC 4565 may be in the aftermath of a period with more intense star formation, likely caused by interaction with one or both satellites. An H I bridge extending from NGC 4565 to IC 3571 also implies that interaction has happened recently in cosmic terms.
NGC 4565, along with NGC 4562, IC 3543, and IC 3546, are listed together as Holm 426 in Erik Holmberg's A Study of Double and Multiple Galaxies Together with Inquiries into some General Metagalactic Problems, published in 1937. It has at least two satellite galaxies, NGC 4562 and IC 3571, one of which is interacting with it. It has a population of roughly 240 globular clusters, more than the Milky Way, and is one of the brightest galaxies of the Coma I Group.
Reader's Guide
NGC 4565 is significant as a prominent edge-on spiral galaxy that serves as a key object for studying galactic structure, warps, and interactions. Its narrow profile makes it a classic example of an edge-on spiral, while its central bar and pseudobulge, confirmed by Spitzer Space Telescope observations, provide insight into the nature of galactic bulges. The detection of a diffuse radio halo and a warp in the radio continuum using LOFAR, along with an estimated minimum age of 130 million years for the warp, offers clues about recent star formation and interactions with satellite galaxies. The presence of an H I bridge to IC 3571 further supports recent interaction. As one of the brightest galaxies in the Coma I Group, NGC 4565 is a benchmark for studying galaxy groups and the dynamics of satellite systems. Its population of roughly 240 globular clusters, exceeding that of the Milky Way, adds to its importance for understanding globular cluster systems. The galaxy's inclusion in Holmberg's 1937 study of multiple galaxies underscores its long-recognized role in extragalactic research.
Did You Know?
- NGC 4565 is more luminous than the Andromeda Galaxy.
- A diffuse radio halo around NGC 4565 was discovered using the LOw-Frequency ARray (LOFAR).
- An H I bridge extends from NGC 4565 to IC 3571, implying recent interaction.
More in Galaxy Clusters and Groups, Part 4 1-24
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