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Date: 22 Sep 2007 21:31:14
From: fvkastro
Subject: Help in identifying object near ARP72
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Hello All,
A couple of weeks ago, I made some images of ARP72. In those images, I
noticed a "vague" object at the coordinates (J2000): RA: 15:46:49 and DEC
17:59:02. The object is not a single star but more of a 'vague blob'.
Looks like a galaxy or a star-cluster.
I downloaded the Digital Sky Survey 2 image to check if the object was
present on their images. Yes it was.
When I load the image in GAIA and superimpose the USNO B.1 database on
it, I can see a lot of stars on those particular coordinates. So perhaps
it is some sort of star cluster? It is definitely not a cluster from the
milky-way halo. No references in the on-line literature however...
If you want fits images or more information, please contact me off-list.
Many thanks for your answers!
Best regards,
fvkastro
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Date: 24 Sep 2007 12:15:37
From: Per Erik Jorde
Subject: Re: Help in identifying object near ARP72
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fvkastro <fvkastro@xs4all.nl > writes:
> A couple of weeks ago, I made some images of ARP72. In those images, I
> noticed a "vague" object at the coordinates (J2000): RA: 15:46:49 and DEC
> 17:59:02. The object is not a single star but more of a 'vague blob'.
> Looks like a galaxy or a star-cluster.
The POSS images clearly shows a galaxy at that position.
> When I load the image in GAIA and superimpose the USNO B.1 database on
> it, I can see a lot of stars on those particular coordinates.
The "stars" are artefacts of the USNO-B1.0 catalog, which has only an
estimated 85% accuracy for distinguishing stars from non-stellar
objects:
http://archive.noao.edu/catalogs/usnob/usno-b.pdf
pej
--
Per Erik Jorde
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Date: 23 Sep 2007 08:56:47
From: fvkastro
Subject: Re: Help in identifying object near ARP72
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On Sun, 23 Sep 2007 08:40:15 +0000, Margo Schulter wrote:
> fvkastro <fvkastro@xs4all.nl> wrote:
>> Hello All,
>>
>> A couple of weeks ago, I made some images of ARP72. In those images, I
>> noticed a "vague" object at the coordinates (J2000): RA: 15:46:49 and
>> DEC 17:59:02. The object is not a single star but more of a 'vague
>> blob'. Looks like a galaxy or a star-cluster.
>
> Hello, there.
>
> When I give these coordinates to fchart for Linux, two objects
> strikingly near the center of the chart are NGC 5994 and NGC 5996,
> galaxies visually very close to each other. Their coordinates in NGC
> 2000.0 are:
>
> NGC 5994 15:46:48 17:51
> NGC 5996 15:46:54 17:52
>
> Note that in NGC 2000.0 RA is given to the nearest tenth of a minute, so
> in converting 15:46.8 and 15:46.9 to your format, I may be exaggerating
> the number of significant digits, a small point.
>
> While I'm not sure if these galaxies represent the "vague" object you
> describe, or if yours is something else about 7' north, I hope that this
> information may be helpful in some way.
>
> Most appreciatively,
>
> Margo Schulter
> mschulter@calweb.com
> Lat. 38.566 Long. -121.430
Hello Margo,
Many thanks for your reply! The NGC5994 / NGC5996 pair are indeed at the
center of the chart because they form ARP72 object. It is a beautiful
combination of two galaxies interacting...
The object I'm looking for (and I also checked the Nasa Extragalactic
Database) is close to this object. approx 1 second in RA and 7 *minutes*
in DEC.
That makes the object all the more mysterious ;-)
Thanks again for helping!
Best regards,
fvkastro
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Date: 23 Sep 2007 21:54:59
From: Margo Schulter
Subject: Re: Help in identifying object near ARP72
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fvkastro <fvkastro@xs4all.nl > wrote:
> Hello Margo,
>
> Many thanks for your reply! The NGC5994 / NGC5996 pair are indeed at the
> center of the chart because they form ARP72 object. It is a beautiful
> combination of two galaxies interacting...
Ah, I guess my initial remarks were more obvious than helpful in solving
the mystery <grin >, although a fine opportunity for me to learn about
the ARP catalogue.
> The object I'm looking for (and I also checked the Nasa Extragalactic
> Database) is close to this object. approx 1 second in RA and 7 *minutes*
> in DEC.
Well, I'm glad that at least I got the 7 arc-minutes of declination about
right. Running fchart again on these coordinates with a DSO limiting
magnitude of 18.0 didn't seem to reveal anything around 7' north of
ARP72 except maybe a star around 9th or 10th magnitude; so this looks
like indeed a "mystery."
> That makes the object all the more mysterious ;-)
>
> Thanks again for helping!
Thank you for your most gracious response, that makes me all the
more eager to learn how the mystery unfolds. I'll stay tuned,
offering you whatever impetus I can lend.
> Best regards,
>
> fvkastro
>
With many thanks,
Margo
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Date: 23 Sep 2007 08:40:15
From: Margo Schulter
Subject: Re: Help in identifying object near ARP72
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fvkastro <fvkastro@xs4all.nl > wrote:
> Hello All,
>
> A couple of weeks ago, I made some images of ARP72. In those images, I
> noticed a "vague" object at the coordinates (J2000): RA: 15:46:49 and DEC
> 17:59:02. The object is not a single star but more of a 'vague blob'.
> Looks like a galaxy or a star-cluster.
Hello, there.
When I give these coordinates to fchart for Linux, two objects strikingly
near the center of the chart are NGC 5994 and NGC 5996, galaxies visually
very close to each other. Their coordinates in NGC 2000.0 are:
NGC 5994 15:46:48 17:51
NGC 5996 15:46:54 17:52
Note that in NGC 2000.0 RA is given to the nearest tenth of a minute, so
in converting 15:46.8 and 15:46.9 to your format, I may be exaggerating
the number of significant digits, a small point.
While I'm not sure if these galaxies represent the "vague" object you
describe, or if yours is something else about 7' north, I hope that
this information may be helpful in some way.
Most appreciatively,
Margo Schulter
mschulter@calweb.com
Lat. 38.566 Long. -121.430
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