ASTRO: NGC 1579

NGC 1579 Image down sampled 0.5x
Perseus
Penryn, California
October 2008
M 250 @ f 9.3 (ag, ST-4)
ST-10XME LRGB - 10 minute subs

A large area of dust. NGC 1579 is a reflection nebula illuminated by
the young and bright emission line star LkH-alpha 101. It is this
star that provides the intense red color.

There is a tendecy to label this nebula as an emission/reflection
nebula. All peer-reviewed scientific studies support the conclusion
that NGC 1579 is a cold cloud of dust reflecting the intense h-alpha
light of 'LkH-alpha 101'.

Redman, et.al. (1986) conducted polarization studies to determine the
illuminating source. The abstract from that study follows;

"The linear polarization of the reflection nebula NGC 1579 and the CO
(1 to 0) emission from the associated molecular gas have been mapped
for several minutes of arc around the exciting star LkH-alpha 101.
These maps show conclusively that LkH-alpha 101 is the sole
significant source of illumination in the region. The dust in the
reflection nebula appears to be uniform over the illuminated region
and is uniformly illuminated by LkH-alpha 101. Despite the patchy
obscuration, the dark cloud which obscures LkH-alpha 101 does not
surround the star. LkH-alpha 101 may have formed out of a placental
cloud whose remnants now include four molecular cloud fragments, two
in front of and two behind the reflection nebula, as well as an H I
cloud previously detected in the region."

Herbirg, et.al. (2004) reports;

"The central region of the dark cloud L1482 is illuminated by LkHalpha
101, a heavily reddened (AV~10 mag) high-luminosity (=8×103 Lsolar)
star having an unusual emission-line spectrum plus a featureless
continuum. About 35 much fainter (mostly between R=16 and 21) Halpha
emitters have been found in the cloud. Their color-magnitude
distribution suggests a median age of about 0.5 Myr, with considerable
dispersion. There are also at least five bright B-type stars in the
cloud, presumably of about the same age; none show the peculiarities
expected of HAeBe stars. Dereddened, their apparent V magnitudes lead
to a distance of about 700 pc. Radio observations suggest that the
optical object LkHalpha 101 is in fact a hot star surrounded by a
small H II region, both inside an optically thick dust shell. The
level of ionization inferred from the shape of the radio continuum
corresponds to a Lyman continuum luminosity appropriate for an early
B-type zero-age main-sequence star. The V-I color is consistent with a
heavily reddened star of that type. However, the optical spectrum does
not conform to this expectation: the absorption lines of an OB star
are not detected. Also, the [O III] lines of an H II region are
absent, possibly because those upper levels are collisionally
deexcited at high densities. There are several distinct contributors
to the optical spectrum of LkHalpha 101. The Halpha emission line is
very strong, with wings extending to about +/-1700 km s-1, which could
be produced by a thin overlying layer of hot electron scatterers.
There is no sign of P Cygni type mass ejection. Lines of Si II are
narrower, while the many Fe II lines are still narrower and are double
with a splitting of about 20 km s-1. Lines of [Fe II], [O I], and [S
II] are similarly sharp but are single, at the same velocity as the Fe
II average. Work by Tuthill et al. allowed the inference, from K-band
interferometry, that the central source is actually a small
horseshoe-shaped arc about 0.05" (35 AU) across. A tipped annulus of
that size in rotation about a 15 Msolar star would produce double
spectrum lines having about the splitting observed for Fe II. The
totality of observational evidence encourages the belief that LkHalpha
101 is a massive star caught in an early evolutionary state."

On 11/12/2010 1:36 PM, glen youman wrote:
NGC 1579 Image down sampled 0.5x
Perseus
Penryn, California
October 2008
M 250 @ f 9.3 (ag, ST-4)
ST-10XME LRGB - 10 minute subs

A large area of dust. NGC 1579 is a reflection nebula illuminated by
the young and bright emission line star LkH-alpha 101. It is this
star that provides the intense red color.

There is a tendecy to label this nebula as an emission/reflection
nebula. All peer-reviewed scientific studies support the conclusion
that NGC 1579 is a cold cloud of dust reflecting the intense h-alpha
light of 'LkH-alpha 101'.

Redman, et.al. (1986) conducted polarization studies to determine the
illuminating source. The abstract from that study follows;

"The linear polarization of the reflection nebula NGC 1579 and the CO
(1 to 0) emission from the associated molecular gas have been mapped
for several minutes of arc around the exciting star LkH-alpha 101.
These maps show conclusively that LkH-alpha 101 is the sole
significant source of illumination in the region. The dust in the
reflection nebula appears to be uniform over the illuminated region
and is uniformly illuminated by LkH-alpha 101. Despite the patchy
obscuration, the dark cloud which obscures LkH-alpha 101 does not
surround the star. LkH-alpha 101 may have formed out of a placental
cloud whose remnants now include four molecular cloud fragments, two
in front of and two behind the reflection nebula, as well as an H I
cloud previously detected in the region."

Herbirg, et.al. (2004) reports;

"The central region of the dark cloud L1482 is illuminated by LkHalpha
101, a heavily reddened (AV~10 mag) high-luminosity (=8×103 Lsolar)
star having an unusual emission-line spectrum plus a featureless
continuum. About 35 much fainter (mostly between R=16 and21) Halpha
emitters have been found in the cloud. Their color-magnitude
distribution suggests a median age of about 0.5 Myr, with considerable
dispersion. There are also at least five bright B-type stars in the
cloud, presumably of about the same age; none show the peculiarities
expected of HAeBe stars. Dereddened, their apparent V magnitudes lead
to a distance of about 700 pc. Radio observations suggest that the
optical object LkHalpha 101 is in fact a hot star surrounded by a
small H II region, both inside an optically thick dust shell. The
level of ionization inferred from the shape of the radio continuum
corresponds to a Lyman continuum luminosity appropriate for an early
B-type zero-age main-sequence star. The V-I color is consistent with a
heavily reddened star of that type. However, the optical spectrum does
not conform to this expectation: the absorption lines of an OB star
are not detected. Also, the [O III] lines of an H II region are
absent, possibly because those upper levels are collisionally
deexcited at high densities. There are several distinct contributors
to the optical spectrum of LkHalpha 101. The Halpha emission line is
very strong, with wings extending to about +/-1700 km s-1, which could
be produced by a thin overlying layer of hot electron scatterers.
There is no sign of P Cygni type mass ejection. Lines of Si II are
narrower, while the many Fe II lines are still narrower and are double
with a splitting of about 20 km s-1. Lines of [Fe II], [O I], and [S
II] are similarly sharp but are single, at the same velocity as the Fe
II average. Work by Tuthill et al. allowed the inference, from K-band
interferometry, that the central source is actually a small
horseshoe-shaped arc about 0.05" (35 AU) across. A tipped annulus of
that size in rotation about a 15 Msolar star would produce double
spectrum lines having about the splitting observed for Fe II. The
totality of observational evidence encourages the belief that LkHalpha
101 is a massive star caught in an early evolutionary state."

This is another I need to revisit. Mine looks horrid compared to this,
especially as to noise and color. Took it as one of my very first
objects after going digital. I had no idea what I was doing back then.
Used only 5 minute subs which just doesn't cut it with only 6 of them.
3 ten minute ones are far better and the 4 I usually use nearly half
the noise of 6 five minute ones and go deeper.

I had a devil of a time with the color. Figured it was my limited
skills, and it was. But at the time hadn't realized it wasn't a true
emission object and was trying to get the h alpha pink that just
wouldn't quite show. Rather than reprocess it I need to redo the data.
Of course our rainy October is just now showing up a month late.
Won't be any imaging for a while if the weather reports are right. Snow
and rain mix for the next two weeks. Did finish getting the blower on
the Ranger ATV today so that should keep the snow at bay for a few more
weeks.

Rick

--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

I first imaged ngc 1579 with film and one look at the result had me
scrambling to find out what type nebula I had imaged, it was obvious
it was not an emission nebula.

There was a French astrophotograper with perhaps the best image I've
seen. I've searched for that image and couldn't find it (google).

Forecast here is for clear skys, of course that will change the day
after full moon.



On Fri, 12 Nov 2010 15:26:54 -0600, Rick Johnson
wrote:

This is another I need to revisit. Mine looks horrid compared to this,
especially as to noise and color. Took it as one of my very first
objects after going digital. I had no idea what I was doing back then.
Used only 5 minute subs which just doesn't cut it with only 6 of them.
3 ten minute ones are far better and the 4 I usually use nearly half
the noise of 6 five minute ones and go deeper.

I had a devil of a time with the color. Figured it was my limited
skills, and it was. But at the time hadn't realized it wasn't a true
emission object and was trying to get the h alpha pink that just
wouldn't quite show. Rather than reprocess it I need to redo the data.
Of course our rainy October is just now showing up a month late.
Won't be any imaging for a while if the weather reports are right. Snow
and rain mix for the next two weeks. Did finish getting the blower on
the Ranger ATV today so that should keep the snow at bay for a few more
weeks.

Rick

Glen, you got a lot more signal than I was able to get of this object so
far. And detail is very good also.

Stefan

"glen youman" schrieb im Newsbeitrag
...
NGC 1579 Image down sampled 0.5x
Perseus
Penryn, California
October 2008
M 250 @ f 9.3 (ag, ST-4)
ST-10XME LRGB - 10 minute subs

A large area of dust. NGC 1579 is a reflection nebula illuminated by
the young and bright emission line star LkH-alpha 101. It is this
star that provides the intense red color.

There is a tendecy to label this nebula as an emission/reflection
nebula. All peer-reviewed scientific studies support the conclusion
that NGC 1579 is a cold cloud of dust reflecting the intense h-alpha
light of 'LkH-alpha 101'.

Redman, et.al. (1986) conducted polarization studies to determine the
illuminating source. The abstract from that study follows;

"The linear polarization of the reflection nebula NGC 1579 and the CO
(1 to 0) emission from the associated molecular gas have been mapped
for several minutes of arc around the exciting star LkH-alpha 101.
These maps show conclusively that LkH-alpha 101 is the sole
significant source of illumination in the region. The dust in the
reflection nebula appears to be uniform over the illuminated region
and is uniformly illuminated by LkH-alpha 101. Despite the patchy
obscuration, the dark cloud which obscures LkH-alpha 101 does not
surround the star. LkH-alpha 101 may have formed out of a placental
cloud whose remnants now include four molecular cloud fragments, two
in front of and two behind the reflection nebula, as well as an H I
cloud previously detected in the region."

Herbirg, et.al. (2004) reports;

"The central region of the dark cloud L1482 is illuminated by LkHalpha
101, a heavily reddened (AV~10 mag) high-luminosity (=8×103 Lsolar)
star having an unusual emission-line spectrum plus a featureless
continuum. About 35 much fainter (mostly between R=16 and 21) Halpha
emitters have been found in the cloud. Their color-magnitude
distribution suggests a median age of about 0.5 Myr, with considerable
dispersion. There are also at least five bright B-type stars in the
cloud, presumably of about the same age; none show the peculiarities
expected of HAeBe stars. Dereddened, their apparent V magnitudes lead
to a distance of about 700 pc. Radio observations suggest that the
optical object LkHalpha 101 is in fact a hot star surrounded by a
small H II region, both inside an optically thick dust shell. The
level of ionization inferred from the shape of the radio continuum
corresponds to a Lyman continuum luminosity appropriate for an early
B-type zero-age main-sequence star. The V-I color is consistent with a
heavily reddened star of that type. However, the optical spectrum does
not conform to this expectation: the absorption lines of an OB star
are not detected. Also, the [O III] lines of an H II region are
absent, possibly because those upper levels are collisionally
deexcited at high densities. There are several distinct contributors
to the optical spectrum of LkHalpha 101. The Halpha emission line is
very strong, with wings extending to about +/-1700 km s-1, which could
be produced by a thin overlying layer of hot electron scatterers.
There is no sign of P Cygni type mass ejection. Lines of Si II are
narrower, while the many Fe II lines are still narrower and are double
with a splitting of about 20 km s-1. Lines of [Fe II], [O I], and [S
II] are similarly sharp but are single, at the same velocity as the Fe
II average. Work by Tuthill et al. allowed the inference, from K-band
interferometry, that the central source is actually a small
horseshoe-shaped arc about 0.05" (35 AU) across. A tipped annulus of
that size in rotation about a 15 Msolar star would produce double
spectrum lines having about the splitting observed for Fe II. The
totality of observational evidence encourages the belief that LkHalpha
101 is a massive star caught in an early evolutionary state."