Halton Arp was interested in taking images on a telescope with higher magnification and collected lists of interesting galaxies from Vorontsov-Velyaminov's catalogue as well as lists from A.G. Wilson & E. Herzog who also had also analysed the Palomar Observatory Sky Survey. He also collected lists from Thorton Page and C.A Wirtanen who analyzed the Lick Position Survey, objects from W.W. Morgan, F. Zwicky, Charles Kowal & Gibson Reaves, as well as plates by Minkowski and Baade from the Mount Wilson Observatory.1
So that proper credit could be given, one of the columns in the table of objects for his atlas included the name of the first observer as best it could be determined. If that object had an associated number it was also given.1
Since then there has been further research done on this pair of galaxies and on UGC01810, the larger galaxy, itself (all the references to papers including the smaller companion, UGC01813, are the same as for the pair). The following links take you to the complete lists of these papers, and following the links provided gives the abstract of the chosen paper and, if available, a link to a page where you may be able to find the full article. (Click on the numeric code and then the link to the ADS Abstract near the bottom of the page)
I will be looking briefly at a couple of these papers, namely the ones that focus most directly on Arp 273 or UGC01810; the papers where they're not one of hundreds of galaxies studied or where there are direct results given. These will be:
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| 'Sloshing in High-Speed Galaxy
Interactions' By Thomas Zeltwanger, Neil F. Comins and Richard V.E. Lovelace From The Astrophysical Journal, 543:669-685, 2000 November 10 |
Abstract:
Observations of lopsided spiral galaxies motivated us to explore whether the rapid passage of a companion galaxy could cause them. We examine whether the center of mass of the visible matter becomes displaced from the center of mass of the dark halo during the intruders passage, thereby causing an asymmetric response and asymmetric structure. Two-dimensional N-body simulations indicate that this can happen. We also explore some consequences of this offset. These include the center of mass of the visible disk following a decaying orbit around the halo center of mass and the development of transient one-armed spirals that persist for up to six rotation periods. We then study the results of a variety of initial conditions based on such offsets. We report on the results of several runs in which we initially offset a disk from its halos center of mass by an amount typical of the above interaction. In some runs the halo is free to move, while in others it is held fixed. We used three different mass distributions for the halo in these runs. We find that the disks center of mass spiraled inward, creating a variety of observed or observable phenomena including one-armed spirals, massive clumps of particles, and counterrotating waves. The systems settle into relatively axisymmetric configurations. Whether or not the end states included a bar depended on a variety of initial conditions.
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'Models
and observations of starbusts. II. Strabursts in interacting
galaxies' By K. Bernlohr From Astronomy and Astrophysics. 268, 25-34, 1993 |
Abstract:
Evolutionary models are applied here to starburst galaxies in a sample of 30 interacting or merged systems in order to determine the duration of the starbursts. The time delay between bursts in both components of interacting pairs of disk galaxies is investigated and it is found that starbursts in the minor galaxies of these pairs started earlier than those in the major galaxies. While strong starbursts are found to be active for only about 2 x 10 exp 7 yrs, the time delay between the bursts in both components of the interacting pairs can be significantly larger. Delays of up to 2 x 10 exp 8 yrs are found in the sample. Model fits show that the mass-to-luminosity ratios of strong central starbursts indicate a deficiency of low-mass stars in the starburst initial mass function. The required low-mass-star deficiency is smaller than previously believed.
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'A
photometric study of interacting galaxies. I.
Observations' By V.P. Reshetnikov, V.A Hagen-Thorn, and V.A. Yakovleva From Astronomy and Astrophysics, Supplement Series 99, 257-289, 1993 | |
Abstract:
As part of an investigation on what effect galaxy-galaxy interaction has on the global photometric properties of the involved galaxies, we present here new photometric data in the Cousins R-prime system for a sample of 35 interacting systems. Isophotes, equivalent profiles, and total magnitudes of all sample galaxies (73) are determined. Our estimates and the comparison with the published results show that the accuracy of our photometry is about 0.2-0.3 mag. A later paper will present the interpretation of the data.
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BVRI imaging of M 51-type pairs II. Bulge
and disk parameters Laurikainen, E.; Salo, H. Astronomy and Astrophysics Supplement, v.141, p.103-111 | |
Abstract:
We present decompositions of azimuthally averaged surface brightness profiles in optical B, V, R and I-bands for a sample of 40 M 51-type interacting galaxies. The profiles were modelled by an exponential disk and a spherical bulge described either by the R1/4 law or by an exponential function. Half of the galaxies were well fitted by both bulge models, whereas for 35 % the exponential function was a better choice. Special care was taken on eliminating superpositions of the companion galaxies. The mean B-band central surface brightness mu_0 was found to be 21.5 mag arcsec-2, which is near to the value originally found by Freeman (\cite{freeman70}), but the scatter was fairly large. Galaxy interactions have strongly modified the disks in many of the galaxies in the sample. For example, six of them had extremely flat brightness profiles outside the exponential part of the disk, and many showed significant isophotal twists. Tables 1 to 4 and Figs. 2 to 4 are only available in the electronic version at http://www.edpsciences.org}
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'Sloshing in High-Speed Galaxy Interactions'
By Thomas Zeltwanger, Neil F. Comins and Richard V.E. Lovelace
The authors of this paper ran computer simulations showing what might happen if the smaller companion galaxy was passing by at high speeds to see if this might account for the asymmetry which is present in the larger companion. From the results they present we see that though not an exact representation they do appear to be on the right track.
"Note the similarity between time step 4.898 in Figures 5 and 6 and the optical image of K64 (Fig. 7)" with K64 being another name for Arp 273. (Also note this images is presented with North up and West to the Left which is different from the rest of my webpage)
Figure 7 -image from NOAO
(for more info
see my Other Telescope Images Page)
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The simulations were created using two-dimensional N-body GALAXY code (credited to Schoeder & Comins 1989, Schoder 1989, and Shorey 1996). There were 100,000 collisionless particles taken to represent stars and "a gravitational halo that compromises 75% of the system's total mass". (This value for the halo was taken as anything more would suppress the formation of bars that might otherwise be present.)
The small companion was taken to be simply a point particle with 20% of the total mass of the galaxy being modeled. The distance between them was however taken to be large enough that if the high-speed companion had realistic dimensions there would be no overlap of the disks. The run which gave a simulation most like Arp 273 (or K64 as it is referred to in the paper) was done using a 'hydrodynamic simulation' for the halo (meaning it was treated like fluid to minimize friction) and a uniform energy density for the gas. Due to physics which I haven't quite worked out yet this means that the temperature of the gas affects it's dynamics. The temperature for this run was taken to be T=5x105K.
What actually appears to occur is that as the spiral arm closest to the intruder is extended the center of mass of the stellar and gas structure moves upwards (conservation of angular momentum). The center of mass of the halo is also affected but less so and so there is a displacement between the two which is was causes the asymmetry. Runs were done at various temperatures and it was show that the the offset caused by the intruder increases with the temperature of the gas.
'Models and observations of starbusts. II. Starbursts in interacting
galaxies'
By K. Bernlohr
To start is probably best to say that a 'Starburst' is a "site of
large scale, extremely high-rate star formation. People aren't positive
about what triggers some reactions but one thing that is known is that it
is often triggered by interactions.
For this study broad band BVRI images and long slit spectra ranging from 3670 to 7400 angstroms were studied. Spectra are the most common data used to try and locate starbursts, they provide so much information that often even the age of the burst can be determined. Current starbursts have strong H-alpha line emission due to the new stars ionizing the surrounding hydrogen, as well as a continuum dominated by O & B type stars (The hottest). A post starburst region has mostly late B and A stars and strong balmer line absorption. Most starbursts tend to last for "only a few" 107 years.
In edge on galaxies such as the smaller companion in Arp 273, however, these spectra aren't as reliable as there is so much obscuration by dust. In this case what is studied is a comparison between the luminosity of the dust, and luminosity in the far infrared (FIR).
Most starbursts occur mainly in the central regions of a galaxy and have a diameter of 1kpc or less. There are cases of extranuclear starbursts but they are far fewer. Arp 273 is not listed as having any extranuclear starbursts in either galaxy but, by the same token, FIR methods are not as reliable for determining this as spectra.
In all of the galaxies studied, very few of the pairs with a mass ratio much different than 1:1 showed starbursts in both galaxies at the same time, and it was always the smaller companion that had the starburst occur first. Why would this happen? Well some of the possible reasons include the fact that the dynamical time scales are shorter, that, in general, smaller galaxies tend to have consumed less of the gas present in the galaxy so there is more 'fuel' available and that the minor companions tend to get more distorted overall in an interaction.
This is the case with Arp 273. The mass ratio is 5:1 and the smaller companion has an active starburst where the larger companion is lying somewhere between having little or no current star formation and having average amounts.
'A photometric study of interacting galaxies. I. Observations'
By V.P. Reshetnikov, V.A Hagen-Thorn, and V.A. Yakovleva
The numerical results presented in this paper can be found on my
spectral analysis page
' BVRI imageing of M 51-type pairs II. Bulge and disk parameters'
Laurikainen, E. and Salo, H.
The numerical results presented in this paper can be found on my
spectral analysis page