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Results from the Lick voorwerpje observations

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In 2010, two Lick 3-m telescope (Kast double spectrograph) observing runs were dedicated to the voorwerpje hunt. The first run served as a follow-up to the results from the initial KPNO 2.1-m survey of likely voorwerpje hosts and the second run added three new objects to the sample, bringing the grand total of confirmed voorwerpjes to 19. This page shows the resulting data products for each Lick target.

 

As with the KPNO spectra page, the positions angles (PA) of the spectrograph are shown for each object - red boxes indicate nuclei; green boxes indicate voorwerpjes. To correlate the galaxy images with the smaller 2D snapshots (directly below the galaxy images, each showing 4 lines: He II, Hβ, and the two big [O III]), mentally rotate each galaxy image so that the white arrow is pointing straight up. A good example to start with is Mrk 266, where the arrow is basically already pointing up. Velocity/flux slices are also shown for each object. An explanation of those can be found here... I'll just note that the x-scale shows projected kiloparsecs along the slit and therefore provides the best way to compare the actual sizes of voorwerpjes/galaxies.

 

Extending wavelength coverage to include the 6300-6750Å rest frame allowed us to diagnose the conditions of the ionized gas via emission line ratios. Certain line ratios reveal things like how ionized the gas is and how hard the ionizing source is. When these ratios are plotted against one another, there is a fairly clear separation between three distinct classes of objects - starbursts, Seyferts, and LINERs. The three most common versions of the diagnostic diagrams are shown here for each object, with the red dots indicating nuclei and green dots indicating voorwerpjes. Nearly all voorwerpje points fall clearly into the Seyfert/AGN region, indicating that we are indeed seeing AGN-ionized gas. Also, the grayscale background is a sample of 30,000 SDSS galaxies for comparison.

 

Nuclear spectra and voorwerpje sample spectra are of course shown along with a zoom-in of whichever warrants a closer look. Typical emission lines are labeled in blue whereas emission lines whose formation require photons of energy greater than 54.4 eV are labeled in purple. The reason for this is that stars typically do not produce such energetic photons, and hence emission lines requiring such energetic photons serve as proof of processes (accretion events around a SMBH for example) too extreme to be explained by stars. Emission line ratios are also listed to the left of [O III] λ5007 in each nucleus/voorwerpje spectrum plot. If the ratio increases from nucleus to voorwerpje, the value for that ratio is colored green. Red text indicates ratios decreasing from nucleus to voorwerpje.

 

 

 

 

 

 

 

 

 

 

 

UGC 11185

Here we have another case of multiple sets of emission lines with slight velocity offsets. Were there an SDSS spectrum for UGC 11185, it would likely have been included in one of the searches for double-peaked [OIII] objects. According to the observations presented here, the other galaxy to the SW also has a Seyfert 2 nucleus.

The voorwerpje here departs from some of the others in that it is clearly a discrete cloud rather than emission simply extending from the nucleus.

Teacup

Teacup is the most distant voorwerpje host included in this study, but certainly not the smallest example in terms of projected extent of emission. The left-hand side of the velocity slice shows the fuchsia-colored 'handle' curving back in toward the 'teacup.'

SDSS 2201+11

SDSS 2201 has twin voorwerpjes and is one of the few cases where the clouds easily outshine the nucleus (see line intensities along the bottom of velocity slice).  Even though it's too faint to see in the 2D spectrum, the data do show weak He II emission over a projected range of 4 kpc or so in the northern cloud.

SDSS 1005+28

It's easy to mix this one up with the SDSS 0955 pair. Again we have two very similar interacting galaxies at z ~ 0.05, and again, one of the galaxies has blue/purple stuff on the side facing away from the other galaxy. Further, intensity of the high-ionization [NeV] line again surpasses that of the low-ionization [OII] line. The main difference however is that SDSS 1005 clearly contains a Seyfert 2 nucleus.

SDSS 0955+39

In terms of literature mentions/inclusion in previous studies, this one was a 'new' find that didn't even have an SDSS spectrum. The most remarkable thing about SDSS 0955's voorwerpje is the strength of [NeV] λ3426 as compared to [OII] λ3727, with the former exceeding the latter comfortably ([NeV]/[OIII] = 1.2). As with IC 2497, the nearest galactic nucleus to the SDSS 0955 voorwerpje appears to be a LINER (based solely on the diagnostic diagrams).

NGC 7212

Not observed by the SDSS and hence not included in the GZ hunt for voorwerpjes, this galaxy was added to the sample based on previous studies which noted extended [O III] emission (HST [O III] images of NGC 7212 and another voorwerpje host, NGC 4388, were presented in this paper). After deciding early on to define a 'voorwerpje' as "AGN-ionized gas extending continuously or discretely (clouds) to distances greater than 10 kpc from the nearest galactic nucleus," we omitted NGC 7212 from the sample.

The image shown here was taken by Dr. Keel at the KPNO 2.1-m telescope (i filter), and I did my best to scale it similarly to the SDSS tiles.

NGC 5972

NGC 5972 is another double lobe radio galaxy which has been mentioned in the literature here and here, after the original radio contour map of the lobes was presented here. Skip to page 44 of that last paper for the contour map (labeled 09946, 1st column, 2nd row) and you may notice something odd. That's right, another instance of radio lobes failing miserably to line up with voorwerpjes....

Mrk 1498

A more accurate spectral classification for Mrk 1498 might be Seyfert 1.85 due to the very obvious enhancement at Hα and the weaker-but-definitely-there enhancement at Hβ. An entire journal paper has been dedicated to Mrk1498, which turns out to be a giant radio galaxy. Strangely, the radio lobes appear to be almost perpendicular to the voorwerpjes.

There is no mystery as to the ionizing source responsible for Mrk 1498's extended emission. Broad Hα is an obvious clue of an active nucleus, but a better clue is detection of coronal lines like [Fe X] λ6375. It takes a whopping 235.04 eV to tear the 10th electron off an iron atom.

Mrk 883

I'm not sure I see the visual counterpart for the faint [O III] emission ~41" to the west of the nucleus. The outer edge of the western loop is ~22" from the nucleus, so that can't be it. Whatever it is, the redshift match between nucleus and faint stuff is too good to be a coincidence.

Mrk 266

Mrk 266 is a great example of what happens when two AGN-hosting galaxies slam together. Our data captured the SW Seyfert 2 nucleus (the other looks more like a LINER in SDSS data), and the brightest part of the blue streamers to the north. Emission at 5007Å extends almost 20 kpc from the SW nucleus.

Although Mrk 266's voorwerpje spectrum closely resembles that of Hanny's Voorwerp, the important difference between the two situations is that there is no real mystery as to the ionization source responsible for Mrk 266's extended emission.

Mrk 78

Mrk 78 is astrophysically significant in the context of searches for binary AGN. As is shown in the nuclear spectrum, there are two sets of emission lines around the Mrk 78's nucleus and each includes the [NeV] λλ3346,3426 lines. In 2011, Fischer et al used Hubble telescope data to show that "it is possible to explain double emission lines with radial velocity offsets seen in AGN similar to Mrk 78 without requiring dual supermassive black holes." 

Our data show that the single AGN in Mrk 78 is plenty powerful enough to ionize gas ~10 kpc away.

Posted by:	stellar190
Other ID:	I Zw 205
Distance:	173 Mpc
SDSS-g Mag:	17.61
[O III] λ5007 extent relative to nucleus:	+11 kpc
	-11 kpc
NED link	SDSS link

Posted by:	Half 65
Other ID:	SDSS J143029.88+133912.0
Distance:	352 Mpc
SDSS-g Mag:	15.77
[O III] λ5007 extent relative to nucleus:	+10 kpc
	-18 kpc
NED link	SDSS link

Posted by:	stellar190
Other ID:	CGCG 428-014
Distance:	124 Mpc
SDSS-g Mag:	14.92
[O III] λ5007 extent relative to nucleus:	+14 kpc
	-15 kpc
NED link	SDSS link

Posted by:	stellar190
Other ID:	n/a
Distance:	213 Mpc
SDSS-g Mag:	17.50
[O III] λ5007 extent relative to nucleus:	+6 kpc
	-11 kpc
NED link	SDSS link

Posted by:	StephanieC
Other ID:	n/a
Distance:	200 Mpc
SDSS-g Mag:	16.50
[O III] λ5007 extent relative to nucleus:	+4 kpc
	-10 kpc
NED link	SDSS link

Other ID:	CGCG 428-032
Distance:	111 Mpc
SDSS-g Mag:	n/a
[O III] λ5007 extent relative to nucleus:	+7 kpc
	-6 kpc
NED link	n/a

Posted by:	NeilGibson
Other ID:	UGC 09946
Distance:	125 Mpc
SDSS-g Mag:	14.38
[O III] λ5007 extent relative to nucleus:	+31 kpc
	-23 kpc
NED link	SDSS link

Posted by:	Budgieye
Other ID:	SBS 1626+518
Distance:	229 Mpc
SDSS-g Mag:	15.38
[O III] λ5007 extent relative to nucleus:	+21 kpc
	-23 kpc
NED link	SDSS link

Posted by:	ElisabethB
Other ID:	VV 807
Distance:	157 Mpc
SDSS-g Mag:	15.26
[O III] λ5007 extent relative to nucleus:	+35 kpc
	-16 kpc
NED link	SDSS link

Posted by:	ElisabethB
Other ID:	NGC 5256
Distance:	118 Mpc
SDSS-g Mag:	17.42
[O III] λ5007 extent relative to nucleus:	+18 kpc
	-8 kpc
NED link	SDSS link

Posted by:	???
Other ID:	KUG 0737+652
Distance:	155 Mpc
SDSS-g Mag:	15.00
[O III] λ5007 extent relative to nucleus:	+17 kpc
	-15 kpc (faint)
NED link	SDSS link

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Recapping, here are the other confirmed voorwerpje hosts:

NGC 4388

Mrk 739

Mrk 273

Mrk 463

SDSS 1524+08

IC 2637

NGC 5252

SDSS 1510+07

UGC 7342