Recent News

  • New Paper Published: A massive multi-phase outflow in HE1353-1917

    Tuesday, May 28, 2019

    A new paper from the CARS team has been published which demonstrates the full diagnostic power of our unique spatially-resolved multi-wavelength data set. The edge-on host galaxy of HE1353-1917 shows a unique orientation of the AGN's ionization cone which is turned towards the disc of the galaxy. A small radio-jet is associated with the ionization cone an extends about 1kpc into the host galaxy. Our spatially-resolved spectroscopy in the optical with MUSE at the VLT, in the NIR with NIFS at Gemini-N and in the sub-mm with ALMA reveals a massive outflow in all those gas phase at the tip of the jet. The energetics of the outflows shows a high mass outflow rate at 1kpc which clearly exceed the star formation rate of the entire galaxy and therefore has the potential to impact the evolution of the galaxy. However, the current SFR is at most mildly reduced which would be restricted to the central 1kpc so far. Energetically, the driven mechanisms of the outflow is not fully clear, but the size of the jet and its directional power suggests that it plays a crucial role for the injection of the energy.

    While this is just a single case study, the CARS team is working on a systematic analysis of the entire CARS sample of AGN host galaxies. A lot of interesting results can be expected.

    Velocity dispersion map in [OIII], H2, and CO(1-0) showing highly turbulent motion associated with a bipolar outflow within the central 1kpc of the AGN host galaxy HE1353-1917.  The spectra in all hot spots reveal a distinct kinematic feature closely associated with a radio jet structure as the likely powering source of the outflow.

  • New Paper Published: [CII] excess in HE1353-1917

    Tuesday, May 28, 2019

    Our PhD student Irina Smirnova-Pinchukova used FIR observations with the flying observatory SOFIA aboard Boeing 747SP to study the [CII] 158µm emission line in a sample of 5 AGN host galaxies from the CARS sample. Irina discovered that, surprisingly, one of the targeted galaxies, named HE1353-1917 at z=0.035, exhibits ten times higher [CII] luminosity than expected from the star formation rate. Hence, there is an additional excitation mechanism at work in this specific galaxy that is injecting additional energy in the ISM which cooling through the [CII] line. A companion paper by the PI of CARS, Bernd Husemann, is discussing the properties of a massive multi-phase AGN-driven outflow on kpc scales also discovered in this galaxy. Since the [CII] excess is confirmed to originate from the galaxy center, Irina argues that the [CII] excess is directly powered by the shocked-heated gas in the outflows. Our observations at low redshift are crucial to interpret [CII] observations of high redshift galaxies with ALMA.

    [CII] 158µm luminosity as a function of FIR luminosity as a proxy for the ongoing star formation rate. All of our CARS targets observed with SOFIA follow the same relation as all galaxies in the local Universe. Only the galaxy HE1353-1917 is clearly deviating from the trend and shows an order of magnitude excess of [CII].

  • New Paper Published: Only flat bars are actively forming stars!

    Wednesday, May 15, 2019

    As part of the CARS survey PhD student Justus Neuman from the Leibniz-Intstitute for Astrophysics in Potsdam systematically studied the star formation along bars in the AGN host galaxies, which has been accepted to be published in the journal A&A. In this work Justus compared the amount of SFR along the bar as traced using the optical Halpha line with morphological properties of the bar as measured through detailed 2D photometric decompositions of the galaxy images. He found that the sample appears bimodal clearly separating into star-forming and non-star-forming bars. In comparison with the surface brightness of the bar, Justus found that only the bars with very flat surface brightness profiles were forming stars. The lack of star formation in less flat bars may be connected also to the presence of inner rings in those galaxies.

    Bars are also thought to be one mechanisms through which gas is funneled towards the center of the galaxy to fuel AGN at their centers. However, no correlation between the star formation rate along the bar with AGN bolometric luminosity was found. Whether such a non-correlation is caused by time-scale difference or implies an insignificant link between bars and AGN fueling remains to be understood in the future.

    Justus work is the first step in characterizing the star formation properties of AGN host galaxies. More work on AGN outflows and potential impact on the star formation will be studied in future CARS publications in more detail.

    Comparison between star formation rate of the bar with the Sersic parameter n which indicates the steepness/flatness of the bars surface brightness profile. The observations show a clear bimodal distribution in SFR and Sersic parameter which highlights that only bars with a very flat surface brightness profile are actively forming stars.

  • First [CII] map taken with SOFIA FIFI-LS published

    Thursday, September 27, 2018

    The CARS team published the first results from the SOFIA FIFI-LS instrument of spatially-resolved [CII] 158micron emission in a nearby luminous AGN host galaxy at redshift z~0.04. The work is led by Dr. G. Busch from the University of Cologne and shows that the [CII] emission largely follows the expectations from the amount and distribution of ongoing star formation in the host galaxy as mapped with the VLT-MUSE integral-field spectrograph at high spatial resolution in the optical. It shows that AGN do not necessarily impact the [CII] excitation, but a larger sample is currently under investigation to confirm this result. The SOFIA FIFI-LS instrument also detected [CII] emission far beyond the host galaxy which has an unknown origin. We speculated that neutral gas in the outskirts of the disc is excited either by the UV background or a diffuse radiation field from the galaxy itself. In summary, the CARS team has successfully shown that the SOFIA airborne observatory is able to capture [CII] emission not only in our Milky Way but also in nearby galaxies out to significant redshifts. The article will appear in the upcoming SOFIA focus issue of the Astrophysical Journal Letters.

    Comparison of the predicted [CII] map from Ha observed with VLT-MUSE and the real [CII] map observed with SOFIA FIFI-LS. The elongated [CII] structure of the prominent star forming bar in this galaxy is well visible even at the limited spatial resolution of SOFIA. The [CII] surface brightness follows nicely previous relations established for star forming galaxies observed with Herschel.

  • 3rd CARS team meeting

    Monday, August 6, 2018

    Twelve CARS team members met again for the annual meeting from 6-10 August 2018 in Heidelberg. We discussed the most recent results related to AGN outflows, star formation in AGN host galaxies, environment and kinematic properties of our 40 AGN host galaxies. Of course our changing-look AGN Mrk1018 got some special attention during the week, but the core of this galaxy still does not want to reveal it secrets. All aspects of our multi-wavelength data was discussed in detail and challenged with all the different experience we cover in the team.Again a hugely productive CARS with lots of exciting science results to be released on all aspect of AGN host galaxies. Stay tuned!

    CARS team members having fun during our 3rd team meeting in Heidelberg. Picture was taken in front of the famous Heidelberg castle on the old bridge of the old town. 

  • No evidence of galaxy-scale hot outflows in two nearby AGN!

    Tuesday, July 3, 2018

    Based on deep Chandra X-ray observations of two nearby AGN (HE0227-0913 and HE0351+0240), M. Powell et al. reported no evidence of galaxy-wide hot gas outflows. After careful analysis of the Chandra PSF to deal with the bright type 1 AGN core, no significant extended emission could be detected. This is a surprising result since current theoretical models predict rather bright X-ray emission from hot gas outflows on kpc-scales powered by the AGN.

    This shows that the prediced outflows are not necessarily ubiquitos in AGN host galaxies. Either the multi-phase gas composition is different than predicited, the AGN is too young to show outflows on large scales, or the AGN is actually not capable of diriving a powerful outflow. Of course, with two objects we cannot systematically explore these effects, but these X-ray observations needed are expensive were done here as a pilot study. We expect that the CARS team is going to obtain additional Chandra observations in the future.

     

    Chandra X-ray images of HE0227-0913 and HE0351+0240 together with their matched simulated PSFs. Below is the X-ray spectrum extracted from the read-out strike that is modelled with a single power-law model.

  • Dimming of Mrk1018 has stopped!

    Wednesday, October 25, 2017

    Our team continued to monitor the changing-look AGN Mrk1018 after its rapid decline. Our new paper led by Mirko Krumpe nicely shows that the dimming of Mrk1018 surprisingly halted by now and has likely reached a minimum in activity. This already rules out some scenarios like a tidal-disruption event. It opens the possibility that Mrk1018 is turning bright again at some point. Our multi-wavelength monitoring of Mrk1018 is therefore continuing and we are expected to present exciting results on this enigmatic AGN in the next years.

    U-band light curve of Mrk1018 after deblending the AGN and host galaxy light using galfit. The strong decline of the changling-look AGN has clearly stopped and shows variabiliy on yearly timescales.

  • 2nd annual meeting of the CARS team

    Thursday, June 1, 2017

    In the week of 29th of May till 2nd of June, 9 brave CARS teamm members met at the Leibniz-Institute for Astrophysics in Potsdam to discuss the progress of the survey, analysis data and preparing upcoming papers. What a productive meeting and a great and enjoyable time for all members of the team. We all thank T. Urrutia and M. Kumpe from the AIP for organizing the fantastic meeting.

    Participants of the CARS team meeting in the front of the 50cm telescope at the AIP.

  • Press releases about extra-ordinary "changing-look" AGN discovery

    Thursday, September 15, 2016

    The publication of the first two CARS papers in A&A about the discovery and nature of the "changing-look" AGN Mrk 1018 are accompanied by several press releases today by ESO, CAASTRO, AIP, and others. The mystery of the rare change in the behaviour of the supermassive black hole at the centre of this distant galaxy has been discovered and solved by the CARS team using ESO’s Very Large Telescope along with the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory. It seems that the black hole has fallen on hard times and is no longer being fed enough fuel to make its surroundings shine.

    The two papers describing the discovery and first detailed investigation of the cause for the dramatic dimming can be found here:

    1) The Close AGN Reference Survey (CARS) - Mrk 1018 returns to the shadows after 30 years as a Seyfert 1, McElroy et al. 2016, A&A, 593, L8

    2) The Close AGN Reference Survey (CARS) - What is causing Mrk 1018’s return to the shadows after 30 years?, Husemann et al. 2016, A&A, 593, L9

     

    For further question please contact either

    Bernd Husemann, European Southern Observatory, bhuseman (AT) eso.org, 0049 89 3200 6750

    Rebecca McElroy, University of Sydney, rmcelroy (AT) physics.usyd.edu.au, 0061 421 882 513

    This image from the SDSS Stripe 82 survey shows the active galaxy Markarian 1018, which has a supermassive black hole at its core. The faint loops of light around the galaxy are a result of its interaction and merger with another galaxy in the recent past. Credit: ESO/CARS survey

  • CARS meets SOFIA for first observations

    Wednesday, March 9, 2016

    Two of the CARS team members recently had the chance to participate on SOFIA science flights in which CARS galaxies are observed with FIFI-LS. PhD student Gerold Busch and CARS team leader Bernd Husemann took-off with SOFIA on March 1 and March 9, respectively, for 10hour long science flights. The Mission: Detecting [CII] in these AGN host galaxies. Despite their low redshift, it is still a challange for SOFIA to get enough signal due to remaining earth atmosphere.  Luckly, [CII] could be detected in the majority of galaxies as planned. Detailed investigations  of the data will start once reduced by the FIFI-LS science teams and we are looking forward for additional data obtained from the southern deployment of SOFIA in Christchurch during July-August.

    Left: CARS team member Gerold Busch in front of SOFIA before departure for an exciting science flight. Right: CARS team leader Bernd Husemann captures in front of the FIFI-LS instrument inside of SOFIA. Both shared the unique experience of flying on this amazing  plane at an altitude of 45000 feet.

Pages