While the blog has reported some off-planet developments in the study of giant gas clouds ionized by active nuclei (voorwerpjes), we also have some news back here on the third rock from the Sun. Despite our expectations from the weather forecasts, a bit more than half the observing time last week at Lick Observatory’s 3-meter Shane telescope was good, so we could have a look at 13 candidates. Some of these turned out to have gas shining in such small regions that it’s not very interesting for our purposes (I mean, less than 10,000 light-years? Really?), and in some cases the features that gave interesting colors in the SDSS composites were due to star formation. But we did add three new giant clouds to our set.

SDSS J100507.88+283038.5 has a type 2 Seyfert nucleus. Its SDSS image showed a very suspicious blue wedge pointing eastward. The spectrum confirmed that this is high-ionization gas which must be seeing a powerful AGN; we spent 2.5 hours collecting data with the spectrograph slit in two different orientations.

SDSS J074241.70+651037.8 = Markarian 78 is another type 2 Seyfert. The presence of extended gas in this one had been noted some years ago, and there are even Hubble spectra offset from the galaxy core. However, there are no Hubble images in visible light, so we fall back on the SDSS picture:

Finally, we come to SDSS J095559.34+395438.9. This may yet prove to be the most interesting of the three. Our spectrum shows a weak Seyfert 2 nucleus there was no SDSS spectrum for this member of the interacting pair). Until reduction of the data is complete, we’re not sure that the gas shows the characteristic He II emission showing that it sees an AGN; if so, this would be another rare case of finding an AGN through extended gas.

On the last night, we lined all the observers up on a service platform in front of the telescope for a team picture: from left, that’s me (the only one not from the University of California, Santa Barbara); grad students Alessandro Sonnenfeld, Anna Pancoast, and Anna Nierenberg; and Vardha Bennert. Fortunately for my fading sanity in the small hours of the morning, Anna and Anna are pronounced differently.

We have these new results in time to fold them in to the poster presentation being prepared by Drew Chojnowski for the next meeting of the American Astronomical Society a month from now in Seattle. There will also be some additional presentations there that will greatly interest Zoo participants; we hope to have exact dates and times in the next day or two.

An especially nice side project of Galaxy Zoo has been uncovering giant gas clouds ionized by active galactic nuclei. Of course, the most striking of these has been Hanny’s Voorwerp, whose study has been fruitful enough! In addition, Zooites proved to be good at finding smaller, dimmer versions (“voorwerpjes”, using the Dutch diminutive form). We harvested these both from Forum postings, and from a targeted hunt of galaxies with known AGN (arranged by Waveney). To be sure what we’re dealing with, we need spectra of these clouds. We had observing runs to do this last summer from Kitt Peak and Lick Observatories, confirming many new cases (some of which may have a similar history of faded glory to what we infer for Hanny’s Voorwerp). Kevin led a further proposal to look at these in X-rays, so we can tell whether the suspiciously dim nuclei are really dim or actually hidden by foreground gas and dust.

We have another observing session this week with the 3-meter Shane telescope of Lick Observatory, a facility of the University of California. The proposal was led by Vardha Nicola Bennert from Santa Barbara, observing as before with UCSB students Anna Pancoast and Chelsea Harris. Here they are standing in front of the telescope’s mirror cell and instrument cluster.

I was also able to arrange going to Mount Hamilton for these four nights. This will be sort of a homecoming for me – as a graduate student at UC Santa Cruz, Lick was where I cut my observational teeth. Checking some old logbooks, I have entries slightly over thirty years ago (and a collection of photos which should shortly be updated!). For my thesis, on the spectra of gas in normal galaxies and whether they contain weak AGN, I used over 70 nights on the then new 1m telescope. So not only was UCSC where I studied interpretation of spectra, but Lick was where I got my first (few hundred) galaxy spectra. Back then, the 3m was the primary telescope for UC astronomers, so graduate students worked with it only while assisting faculty members. I did manage to spend a few hours at the prime focus of the 3m while we were working on what might have been the observatory’s first CCD spectrograph (constructed by painful use of a hacksaw on one originally built for Margaret Burbidge to use image tubes with). We looked at a planetary nebula for wavelength calibration, giving me a lasting memory of just how green the [O III] emission lines appear. (I also managed to see the radio galaxy Cygnus A through the eyepiece while lining up the spectrograph slit). Another student and I managed to get allocated a single otherwise unused night of 3m time to split – and it snowed. Here’s documentation – that young-looking guy is in the cage sitting in the middle of the telescope at the top of the tube. This was such a stopgap setup that the only way to refill the CCD’s liquid nitrogen involved running a long tube between circuit boards of the control electronics. I categorically deny ever having dumped liquid nitrogen on my advisor. Almost.

Times have changed. Everything is remotely operated, and not only do CCDs rule, but the Kast double spectrograph uses a dichroic beamsplitter to separate blue and red light so that each goes into a separate spectrograph and CCD optimized for that part of the spectrum. We’re ready with a list of target galaxies winnowed down by reanalysis of the SDSS images after selection by Zooites. If last summer’s set is a guide, at least half of these will prove to have huge, galaxy-sized clouds illuminated by seen or unseen nuclei. I hope to get the results processed quickly; at the Seattle meeting of the American Astronomical Society in January, there will be a display presentation from last summer’s work led by Drew Chojnowski, and it would be great to double our sample size.

Of course, as with any ground-based observations, we will be at the mercy of the weather. You can keep track using the especially crisp webcam views provided by Lick (one of which looks across the brilliant city lights of the whole San Francisco Bay area, which have been kept slightly under control by extensive light-pollution lobbying but made Lick astronomers some of the first to use digital sky subtraction for spectra). And of course we’ll keep the Zoo updated on our data.