NGC 4622

NGC 4622
A Hubble Space Telescope (HST) image of NGC 4622.
Observation data (J2000 epoch)
Constellation	Centaurus
Right ascension	12^h 42^m 37.7^s^[1]
Declination	−40° 44′ 35″^[1]
Redshift	4367 ± 39 km/s^[1]
Distance	111 million ly
Apparent magnitude (V)	12.6^[1]
Characteristics
Type	SA(r)ab^[1]
Apparent size (V)	1′.7 × 1′.6^[1]
Other designations
PGC 42701^[1]

An illustration showing the major components of NGC 4622

A simulation of the NGC 4622 arm pairs, exhibiting the Fourier transform m = 2.

NGC 4622 is a face-on unbarred spiral galaxy with a very prominent ring structure located in the constellation Centaurus.

Spiral structure

The spiral galaxy, NGC4622 (also called backward galaxy), lies 111 million light years away in the constellation Centaurus. NGC 4622 is an example of a galaxy with leading spiral arms.^[2] In spiral galaxies, spiral arms were thought to trail; the tips of the spiral arms winding away from the center of the galaxy in the direction of the disks orbital rotation. In NGC4622, however, the outer arms are leading spiral arms; the tips of the spiral arms point towards the direction of disk rotation. This may be the result of a gravitational interaction between NGC 4622 and another galaxy or the result of a merger between NGC 4622 and a smaller object.^[2]

NGC 4622 also has a single inner trailing spiral arm.^[2] Although it was originally suspected that the inner spiral arm was a leading arm, the observations that established that the outer arms were leading also established that the inner arm was trailing.^[2]

These results were met with skepticism in part because they contradicted conventional wisdom with one quote being “so you’re the backward astronomers who found the backward galaxy.” The fact that a pair of arms could lead was not easy to accept. Astronomical objections centered on the fact that dust reddening and cloud silhouettes were used to determine that the outer arms led. The galaxy disk is tilted only 19 degrees from face-on making near to far-side effects of dust hard to discern and because clumpy dust clouds might be concentrated on one side of the disk, creating misleading results.

In response, the “backward astronomers” determined^[3] NGC4622’s spiral arm sense with a method independent of the previous work. The new Fourier component method is actually assisted by the small tilt, and dust reddening and cloud silhouettes are not used in the latest analysis. The Fourier component method reveals two new weak arms in the inner disk winding opposite the outer strong clockwise pair. Thus the galaxy must have a pair of arms winding in the opposite direction from most galaxies. Analysis of a color-age star formation angle sequence of the Fourier components establishes that the strong outer pair is the leading pair.

While the presence of backward arms in a galaxy may seem like an inconvenient truth to many, two independent methods now indicate that NGC4622’s arms do indeed behave in a very unusual fashion, with the outer arms winding outward in the same direction the disk turns.

A Fourier component image of the arm pairs is shown with one of the pair of arms marked for the newly discovered inner CCW pair (black dots) as well as one of the already known (CW) outer pair (white dots).

External links

References

1 2 3 4 5 6 7 "NASA/IPAC Extragalactic Database". Results for NGC 4622. Retrieved 2007-03-30.
1 2 3 4 R. J. Buta; G. G. Byrd; T. Freeman (2003). "The Ringed Spiral Galaxy NGC 4622. I. Photometry, Kinematics, and the Case for Two Strong Leading Outer Spiral Arms". Astronomical Journal. 125 (2): 634–666. arXiv:astro-ph/0211002. Bibcode:2003AJ....125..634B. doi:10.1086/345821.
↑ G. G. Byrd; T. Freeman; S. Howard; R. J. Buta (2008). "The Ringed Spiral Galaxy NGC4622. II. An Independent Determination that the Two Outer Arms Lead.". Astronomical Journal. 135 (1): 408–413. Bibcode:2008AJ....135..408B. doi:10.1088/0004-6256/135/1/408.

New General Catalogue 4500 to 4999

NGC 4500 NGC 4501 NGC 4502 NGC 4503 NGC 4504 NGC 4505 NGC 4506 NGC 4507 NGC 4508 NGC 4509 NGC 4510 NGC 4511 NGC 4512 NGC 4513 NGC 4514 NGC 4515 NGC 4516 NGC 4517 NGC 4518 NGC 4519 NGC 4520 NGC 4521 NGC 4522 NGC 4523 NGC 4524 NGC 4525 NGC 4526 NGC 4527 NGC 4528 NGC 4529 NGC 4530 NGC 4531 NGC 4532 NGC 4533 NGC 4534 NGC 4535 NGC 4536 NGC 4537 NGC 4538 NGC 4539 NGC 4540 NGC 4541 NGC 4542 NGC 4543 NGC 4544 NGC 4545 NGC 4546 NGC 4547 NGC 4548 NGC 4549 NGC 4550 NGC 4551 NGC 4552 NGC 4553 NGC 4554 NGC 4555 NGC 4556 NGC 4557 NGC 4558 NGC 4559 NGC 4560 NGC 4561 NGC 4562 NGC 4563 NGC 4564 NGC 4565 NGC 4566 NGC 4567 NGC 4568 NGC 4569 NGC 4570 NGC 4571 NGC 4572 NGC 4573 NGC 4574 NGC 4575 NGC 4576 NGC 4577 NGC 4578 NGC 4579 NGC 4580 NGC 4581 NGC 4582 NGC 4583 NGC 4584 NGC 4585 NGC 4586 NGC 4587 NGC 4588 NGC 4589 NGC 4590 NGC 4591 NGC 4592 NGC 4593 NGC 4594 NGC 4595 NGC 4596 NGC 4597 NGC 4598 NGC 4599 NGC 4600 NGC 4601 NGC 4602 NGC 4603 NGC 4604 NGC 4605 NGC 4606 NGC 4607 NGC 4608 NGC 4609 NGC 4610 NGC 4611 NGC 4612 NGC 4613 NGC 4614 NGC 4615 NGC 4616 NGC 4617 NGC 4618 NGC 4619 NGC 4620 NGC 4621 NGC 4622 NGC 4623 NGC 4624 NGC 4625 NGC 4626 NGC 4627 NGC 4628 NGC 4629 NGC 4630 NGC 4631 NGC 4632 NGC 4633 NGC 4634 NGC 4635 NGC 4636 NGC 4637 NGC 4638 NGC 4639 NGC 4640 NGC 4641 NGC 4642 NGC 4643 NGC 4644 NGC 4645 NGC 4646 NGC 4647 NGC 4648 NGC 4649 NGC 4650 NGC 4651 NGC 4652 NGC 4653 NGC 4654 NGC 4655 NGC 4656 NGC 4657 NGC 4658 NGC 4659 NGC 4660 NGC 4661 NGC 4662 NGC 4663 NGC 4664 NGC 4665 NGC 4666 NGC 4667 NGC 4668 NGC 4669 NGC 4670 NGC 4671 NGC 4672 NGC 4673 NGC 4674 NGC 4675 NGC 4676 NGC 4677 NGC 4678 NGC 4679 NGC 4680 NGC 4681 NGC 4682 NGC 4683 NGC 4684 NGC 4685 NGC 4686 NGC 4687 NGC 4688 NGC 4689 NGC 4690 NGC 4691 NGC 4692 NGC 4693 NGC 4694 NGC 4695 NGC 4696 NGC 4697 NGC 4698 NGC 4699 NGC 4700 NGC 4701 NGC 4702 NGC 4703 NGC 4704 NGC 4705 NGC 4706 NGC 4707 NGC 4708 NGC 4709 NGC 4710 NGC 4711 NGC 4712 NGC 4713 NGC 4714 NGC 4715 NGC 4716 NGC 4717 NGC 4718 NGC 4719 NGC 4720 NGC 4721 NGC 4722 NGC 4723 NGC 4724 NGC 4725 NGC 4726 NGC 4727 NGC 4728 NGC 4729 NGC 4730 NGC 4731 NGC 4732 NGC 4733 NGC 4734 NGC 4735 NGC 4736 NGC 4737 NGC 4738 NGC 4739 NGC 4740 NGC 4741 NGC 4742 NGC 4743 NGC 4744 NGC 4745 NGC 4746 NGC 4747 NGC 4748 NGC 4749 NGC 4750 NGC 4751 NGC 4752 NGC 4753 NGC 4754 NGC 4755 NGC 4756 NGC 4757 NGC 4758 NGC 4759 NGC 4760 NGC 4761 NGC 4762 NGC 4763 NGC 4764 NGC 4765 NGC 4766 NGC 4767 NGC 4768 NGC 4769 NGC 4770 NGC 4771 NGC 4772 NGC 4773 NGC 4774 NGC 4775 NGC 4776 NGC 4777 NGC 4778 NGC 4779 NGC 4780 NGC 4781 NGC 4782 NGC 4783 NGC 4784 NGC 4785 NGC 4786 NGC 4787 NGC 4788 NGC 4789 NGC 4790 NGC 4791 NGC 4792 NGC 4793 NGC 4794 NGC 4795 NGC 4796 NGC 4797 NGC 4798 NGC 4799 NGC 4800 NGC 4801 NGC 4802 NGC 4803 NGC 4804 NGC 4805 NGC 4806 NGC 4807 NGC 4808 NGC 4809 NGC 4810 NGC 4811 NGC 4812 NGC 4813 NGC 4814 NGC 4815 NGC 4816 NGC 4817 NGC 4818 NGC 4819 NGC 4820 NGC 4821 NGC 4822 NGC 4823 NGC 4824 NGC 4825 NGC 4826 NGC 4827 NGC 4828 NGC 4829 NGC 4830 NGC 4831 NGC 4832 NGC 4833 NGC 4834 NGC 4835 NGC 4836 NGC 4837 NGC 4838 NGC 4839 NGC 4840 NGC 4841 NGC 4842 NGC 4843 NGC 4844 NGC 4845 NGC 4846 NGC 4847 NGC 4848 NGC 4849 NGC 4850 NGC 4851 NGC 4852 NGC 4853 NGC 4854 NGC 4855 NGC 4856 NGC 4857 NGC 4858 NGC 4859 NGC 4860 NGC 4861 NGC 4862 NGC 4863 NGC 4864 NGC 4865 NGC 4866 NGC 4867 NGC 4868 NGC 4869 NGC 4870 NGC 4871 NGC 4872 NGC 4873 NGC 4874 NGC 4875 NGC 4876 NGC 4877 NGC 4878 NGC 4879 NGC 4880 NGC 4881 NGC 4882 NGC 4883 NGC 4884 NGC 4885 NGC 4886 NGC 4887 NGC 4888 NGC 4889 NGC 4890 NGC 4891 NGC 4892 NGC 4893 NGC 4894 NGC 4895 NGC 4896 NGC 4897 NGC 4898 NGC 4899 NGC 4900 NGC 4901 NGC 4902 NGC 4903 NGC 4904 NGC 4905 NGC 4906 NGC 4907 NGC 4908 NGC 4909 NGC 4910 NGC 4911 NGC 4912 NGC 4913 NGC 4914 NGC 4915 NGC 4916 NGC 4917 NGC 4918 NGC 4919 NGC 4920 NGC 4921 NGC 4922 NGC 4923 NGC 4924 NGC 4925 NGC 4926 NGC 4927 NGC 4928 NGC 4929 NGC 4930 NGC 4931 NGC 4932 NGC 4933 NGC 4934 NGC 4935 NGC 4936 NGC 4937 NGC 4938 NGC 4939 NGC 4940 NGC 4941 NGC 4942 NGC 4943 NGC 4944 NGC 4945 NGC 4946 NGC 4947 NGC 4948 NGC 4949 NGC 4950 NGC 4951 NGC 4952 NGC 4953 NGC 4954 NGC 4955 NGC 4956 NGC 4957 NGC 4958 NGC 4959 NGC 4960 NGC 4961 NGC 4962 NGC 4963 NGC 4964 NGC 4965 NGC 4966 NGC 4967 NGC 4968 NGC 4969 NGC 4970 NGC 4971 NGC 4972 NGC 4973 NGC 4974 NGC 4975 NGC 4976 NGC 4977 NGC 4978 NGC 4979 NGC 4980 NGC 4981 NGC 4982 NGC 4983 NGC 4984 NGC 4985 NGC 4986 NGC 4987 NGC 4988 NGC 4989 NGC 4990 NGC 4991 NGC 4992 NGC 4993 NGC 4994 NGC 4995 NGC 4996 NGC 4997 NGC 4998 NGC 4999

Astronomical catalog List of NGC objects

This article is issued from Wikipedia - version of the 7/26/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.

NGC 4622

Spiral structure

See also

External links

References