Zooniverse

Abstract:

We use Galaxy Zoo 2 visual classifications to study the morphological signatures of interaction between similar-mass galaxy pairs in the Sloan Digital Sky Survey. We find that many observable features correlate with projected pair separation; not only obvious indicators of merging, disturbance and tidal tails, but also more regular features, such as spiral arms and bars. These trends are robustly quantified, using a control sample to account for observational biases, producing measurements of the strength and separation scale of various morphological responses to pair interaction. For example, we find that the presence of spiral features is enhanced at scales < 70 h^-1 kpc, probably due to both increased star formation and the formation of tidal tails. On the other hand, the likelihood of identifying a bar decreases significantly in pairs with separations < 30 h^-1 kpc, suggesting that bars are suppressed by close interactions between galaxies of similar mass. We go on to show how morphological indicators of physical interactions provide a way of significantly refining standard estimates for the frequency of close pair interactions, based on velocity offset and projected separation. The presence of loosely wound spiral arms is found to be a particularly reliable signal of an interaction, for projected pair separations up to ~100 h^-1 kpc. We use this indicator to demonstrate our method, constraining the fraction of low-redshift galaxies in truly interacting pairs, with M_* > 10^9.5 M_Sun and mass ratio < 4, to be between 0.4 - 2.7 per cent.

Abstract:

We present the Spitzer Extragalactic Representative Volume Survey (SERVS), an 18 square degrees medium-deep survey at 3.6 and 4.5 microns with the post-cryogenic Spitzer Space Telescope to ~2 microJy (AB=23.1) depth of five highly observed astronomical fields (ELAIS-N1, ELAIS-S1, Lockman Hole, Chandra Deep Field South and XMM-LSS). SERVS is designed to enable the study of galaxy evolution as a function of environment from z~5 to the present day, and is the first extragalactic survey both large enough and deep enough to put rare objects such as luminous quasars and galaxy clusters at z>1 into their cosmological context. SERVS is designed to overlap with several key surveys at optical, near- through far-infrared, submillimeter and radio wavelengths to provide an unprecedented view of the formation and evolution of massive galaxies. In this paper, we discuss the SERVS survey design, the data processing flow from image reduction and mosaicing to catalogs, as well as coverage of ancillary data from other surveys in the SERVS fields. We also highlight a variety of early science results from the survey.

Abstract:

We present Hubble Space Telescope imaging and spectroscopy for the extended high-ionization cloud known as Hanny's Voorwerp, near the spiral galaxy IC 2497. WFC3 images show complex dust absorption near the nucleus of IC 2497. STIS spectra show a type 2 Seyfert AGN of rather low luminosity. The ionization parameter log U = -3.5 is in accord with its weak X-ray emission. We find no high-ionization gas near the nucleus, adding to evidence that the AGN is currently at low radiative output (perhaps now dominated by kinetic energy). The nucleus is accompanied by an expanding ring of ionized gas 500 pc in projected diameter on the side opposite Hanny's Voorwerp, with Doppler offset 300 km/s from the nucleus (kinematic age < 7 x10^5 years). [O III] and H-alpha + [N II] images show fine structure in Hanny's Voorwerp, with limb-brightened sections and small areas where H-alpha is strong. We identify these as regions ionized by recent star formation, in contrast to the AGN ionization of the entire cloud. These candidate "normal" H II regions contain blue continuum objects, whose colors are consistent with young stellar populations; they appear only in a 2-kpc region toward IC 2497 in projection. The ionization-sensitive ratio [O III]/H-alpha shows no discernible pattern near the prominent "hole" in the ionized gas. The independence of ionization and surface brightness suggests that substantial spatial structure remains unresolved, to such an extent that the surface brightness sample the number of denser filaments rather than the characteristic density in emission regions. These results fit with our picture of an ionization echo from an AGN whose ionizing luminosity has dropped by a factor > 100 (and possibly much more) within the last 1-2 x 10^5 years; we suggest a sequence of events and discuss implications of such rapid fluctuations for AGN demographics. (Abridged)

Abstract:

We present the results from a Chandra pilot study of 12 massive galaxy mergers selected from Galaxy Zoo. The sample includes major mergers down to a host galaxy mass of 10$^{11}$ $M_\odot$ that already have optical AGN signatures in at least one of the progenitors. We find that the coincidences of optically selected active nuclei with mildly obscured ($N_H \lesssim 1.1 \times 10^{22}$ cm$^{-2}$) X-ray nuclei are relatively common (8/12), but the detections are too faint ($< 40$ counts per nucleus; $f_{2-10 keV} \lesssim 1.2 \times 10^{-13}$ erg s$^{-1}$ cm$^{-2}$) to reliably separate starburst and nuclear activity as the origin of the X-ray emission. Only one merger is found to have confirmed binary X-ray nuclei, though the X-ray emission from its southern nucleus could be due solely to star formation. Thus, the occurrences of binary AGN in these mergers are rare (0-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.

Abstract:

We present the results from a search of data from the first 33.5 days of the Kepler science mission (Quarter 1) for exoplanet transits by the Planet Hunters citizen science project. Planet Hunters enlists members of the general public to visually identify transits in the publicly released Kepler light curves via the World Wide Web. Over 24,000 volunteers reviewed the Kepler Quarter 1 data set. We examine the abundance of \geq 2 R\oplus planets on short period (< 15 days) orbits based on Planet Hunters detections. We present these results along with an analysis of the detection efficiency of human classifiers to identify planetary transits including a comparison to the Kepler inventory of planet candidates. Although performance drops rapidly for smaller radii, \geq 4 R\oplus Planet Hunters \geq 85% efficient at identifying transit signals for planets with periods less than 15 days for the Kepler sample of target stars. Our high efficiency rate for simulated transits along with recovery of the majority of Kepler \geq 4 R\oplus planets suggest suggests the Kepler inventory of \geq 4 R\oplus short period planets is nearly complete.