The research team also uses GMOS IFU spectra to measure line ratios in these regions — to probe their ionization mechanisms and look for kinematic evidence of outflows marked by large ( often bipolar ) velocity ranges or other phenomena .
The team ’ s results confirm what was hinted at by earlier , and less complete data ( by the same team ), that these fading AGN are structurally different from radio-loud AGN , which are dominated by outflows . Instead , these fading AGN are dominated by rotation and consist largely of externally illuminated tidal debris ( Figure 2 ); the Gemini data show a shifting of the [ O III ] emission line due to the gas cloud ’ s rotation .
This work appears in The Astrophysical Journal , and the paper can be found here .
Also read this Galaxy Zoo blog posting describing this work .
Rocky Planets Assembling in a Dwarf Binary System
To date , almost all of the known planetary systems that include a white dwarf are single stars . Now , a team studying SDSS 1557 ( a white dwarf and brown dwarf binary system ) using the Gemini South telescope and the European Southern Observatory ’ s Very Large Telescope , have made a surprising discovery that changes this old perception and opens a new window onto exoplanet formation .
Using GMOS spectra , Jay Farihi ( University College London ) and colleagues identified critical metal features in the system ’ s spectrum as well as the higher Balmer lines . In contrast to the carbon-rich icy material
April 2017 commonly found in double star systems , the planetary material identified in the SDSS 1557 system has a high metal content , including silicon and magnesium . These elements were identified as the debris flowed from its orbit onto the surface of the white dwarf , polluting it temporarily with at least 10 17 grams ( or 1.1 trillion US tons ) of matter , equating it to an asteroid at least 4 kilometers in size .
Farihi says : “ Building rocky planets around two suns is a challenge because the gravity of both stars can push and pull tremendously , preventing bits of rock and dust from sticking together and growing into full-fledged planets . With the discovery of asteroid debris in the SDSS 1557 system , we see clear signatures of rocky planet assembly via large asteroids that formed , helping us understand how rocky exoplanets are made in double star systems .”
The discovery came as a complete surprise , as the team assumed the dusty white dwarf was a single star , but co-investigator Steven Parsons ( University of Valparaíso and University of Sheffield ), an expert in binary systems , noticed the tell-tale signs of something unusual . “ We know of thousands of binaries similar to SDSS 1557 , but this is the first time we ’ ve seen asteroid debris
GeminiFocus
Figure 2 . [ O III ] emission-line profiles from the GMOS IFU spectra overlaid on the HST [ O III ] images for Mkn 1498 , one of the galaxies studied in this work . This galaxy displays a ringlike emission feature dominated by rotation with a velocity range of ± 175 km / sec , ( the 700 km / sec referenced in the legend refers to the entire velocity range shown in each miniature line profile plot ).
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