Recent Results of the MPE Infrared/Submillimeter Group
KMOS3D survey of spatially-resolved gas kinematics, star formation, and ISM properties sheds new light on the physics of galaxy evolution
Our comprehensive and highly successful multi-year KMOS3D survey takes advantage of the efficient multiplexing of the new near-IR 24-IFU KMOS instrument at the Very Large Telescope to spatially resolve the ionized gas kinematics, star formation, outflows, excitation, and metallicities of a large and homogeneous sample of z ~ 0.7 − 2.7 mass-selected galaxies. KMOS3D is a 75-night Garanteed Time Program begun in November 2013 and led jointly by the MPE IR/Submm group and MPE/OPINAS+USM. After 2.5 years and 52 nights of productive observing campaigns, the sample has now reached 564 galaxies, with an overall Hα detection fraction of 80% (and as high as 90% for main-sequence star-forming galaxies). The survey is carried out in well-studied extragalactic fields, benefitting from extensive multi-wavelength data that include the far-IR Herschel PEP survey and high-resolution near-IR/optical grism and imaging data from the 3D-HST/CANDELS HST Treasury programs. KMOS3D is designed to provide an unbiased census from deep integrations (~ 5h − 25h) of the Hα+[NII]+[SII] line emission resolved on seeing-limited scales of 4 − 5 kpc, over a wide range of galaxy parameters and 5 billion years of cosmic time. The strategy is uniquely enabling faint line emission mapping in individual objects and pushing near-IR IFU studies into new regimes such as lower mass star-forming galaxies, and high-mass sub-main sequence galaxies in the process of quenching. Our results, with highlights shown in the Figure, now 1) robustly confirm the earlier findings from our SINS/zC-SINF near-IR IFU survey with SINFONI on the majority of disks among high-z star-forming galaxies and their elevated gas turbulence compared to present-day spirals, and on the ubiquity and origin of powerful AGN- and star formation-driven gas outflows, 2) provide new constraints on the angular momenta, baryonic mass fractions, outer disk structure, mass-metallicity-star formation relation, and gas-phase O/H abundance gradients, and 3) shed new light on dense core formation and star formation quenching in high-mass galaxies.
- Wisnioski et al. 2015, ApJ, 799, 209
- Burkert et al. 2016, ApJ, in press (arXiv:1510.03262)
- Wuyts, S. et al. 2016, ApJ, submitted (arXiv:1603.03432)
- Wuyts, E. et al. 2016, ApJ, in press (arXiv:1603.01139)
Combined CO and dust scaling relations of depletion time and molecular gas fractions with cosmic time, specific star-formation rate, and stellar mass
To measure the gas content of galaxies up to redshifts beyond 2 we apply two independent methods to large samples: First, we use molecular gas masses inferred from CO emission in 500 star-forming galaxies (SFGs) , from the IRAM-COLDGASS, PHIBSS1/2, and other surveys. Second, we derive gas masses from Herschel far-IR dust measurements in 512 galaxy stacks over the same stellar mass/redshift range. The CO- and dust-based results agree remarkably well. We constrain the scaling relations of molecular gas depletion timescale (t depl) and gas to stellar mass ratio (M mol gas/M* ) of SFGs near the star formation "main-sequence" with redshift, specific star-formation rate (sSFR), and stellar mass (M* ). This suggests that the CO → H2 mass conversion factor varies little within ±0.6 dex of the main sequence (sSFR(ms, z, M *)), and less than 0.3 dex throughout this redshift range. This study builds on and strengthens the results of earlier work. We find that t depl scales as (1 + z)–0.3 × (sSFR/sSFR(ms, z, M *))–0.5, with little dependence on M *. The resulting steep redshift dependence of M mol gas/M * ≈ (1 + z)3 mirrors that of the sSFR and probably reflects the gas supply rate. The decreasing gas fractions at high M* are driven by the flattening of the SFR-M * relation. With these new relations it is now possible to determine M mol gas with an accuracy of ±0.1 dex in relative terms, and ±0.2 dex including systematic uncertainties.
- Research paper: Genzel et al. 2015 ApJ 800, 20
Evidence for widespread AGN-driven outflows in the most massive z~1-2 star-forming galaxies
Very deep laser guide star assisted adaptive optics observations have allowed us to detect ubiquitous powerful nuclear outflows in massive (1011 MSun) z ∼ 2 star-forming galaxies, which are plausibly driven by an active galactic nucleus (AGN). The spectra in their central regions exhibit a broad component in Hα and forbidden [N II] and [S II] line emission, with typical velocity FWHM ∼ 1500 km s-1, high [NII]/Hα ratio ≈ 0.6, and intrinsic extent of 2–3 kpc. At larger radii, weaker and less wide broad components suggest star formation driven outflows. The high inferred nuclear mass outflow rates and frequent occurrence suggest that the nuclear outflows efficiently expel gas out of the centers of the galaxies with high duty cycles and may thus contribute to the process of star formation quenching in massive galaxies. Extending to a large sample observed without adaptive optics, we find that the incidence of the most massive galaxies with broad nuclear components is at least as large as that of AGNs identified by X-ray, optical, infrared, or radio indicators, as expected for rapidly varying AGN whose outflows are visible with larger duty cycle than X-ray or optical continuum. The mass loading of the nuclear outflows is near unity. Our findings provide compelling evidence for powerful, high-duty cycle, AGN-driven outflows near the Schechter mass, and acting across the peak of cosmic galaxy formation.
- Research paper: Förster Schreiber et al. 2014 ApJ 787, 38
- Research paper: Genzel et al. 2014 ApJ 796, 7
Molecular gas, extinction, star formation and kinematics in the z=1.5 star forming galaxy EGS130111661
As a follow-up to the high-redshift molecular gas survey PHIBBS (Tacconi et al. 2013; see news item below), a detailed study was performed of one of the most massive galaxies in this survey. For the study of the galaxy named EGS13011166, CO 3-2 line observations from the IRAM Plateau de Bure millimeter interferometer were combined with Large Binocular Telescope (LBT) LUCI observations of the H-alpha line in this galaxy, at matched spatial resolutions of 0.75 arcseconds. The galaxy was scanned perpendicular to the slit with LUCI to obtain spatially resolved spectra both along and perpendicular to the slit. Additionally, Hubble Space Telescope (HST) V-I-J-H band maps were used. Together these data allow to derive the stellar surface density and star formation rate, molecular gas surface density, optical extinction and gas kinematics.
- Research paper: Genzel et al. 2013, The Astrophysical Journal 778, 68
Discovery of a comet factory in a protoplanetary disk with ALMA
June 7, 2013
Using the new Atacama Large Millimeter/submillimeter Array (ALMA), a huge asymmetry has been found in the mm emission from a dust disk surrounding a young star. In contrast, the gas and micron-sized dust grains show a full ring. The data strongly suggests the presence of a dust trap around 60 AU from the star where dust particles can grow by clumping together. This is the first time that such a dust trap has been clearly observed and modelled. It solves a long-standing mystery about how dust particles in disks grow to larger sizes so that they can eventually form comets, planets and other rocky bodies. The images also demonstrate the excellent quality of ALMA data even at the highest frequencies (690 GHz, 0.45 mm, Band 9).
- Research paper: van der Marel, van Dishoeck, Bruderer et al. 2013, Science, 340, 1199
- ESO press release
The relation between molecular gas and star formation over half the cosmic time
April 16, 2013
An unprecedented survey of molecular gas at high redshift provides 52 CO detections in two redshift slices at a redshift z of about 1.2 and 2.2, with stellar masses (M_star) above 10^10.4 solar masses (M_sun) and star formation rates (SFR) above 10^1.5 M_sun per year. The survey is named PHIBSS which stands for the IRAM Plateau de Bure high-z blue sequence CO 3–2 survey of the molecular gas properties in massive, main-sequence star-forming galaxies (SFGs) near the cosmic star formation peak. Including a correction for the incomplete coverage of the M_star – SFR plane, and adopting a "Galactic" value for the CO–H2 conversion factor, average gas fractions are inferred of about 0.33 at z of about 1.2 and about 0.47 at z of about 2.2. Gas fractions drop with stellar mass, in agreement with cosmological simulations including strong star formation feedback. Most of the SFGs between redshifts of about 1 and 3 are rotationally supported turbulent disks. The sizes of CO and UV/optical emission are comparable. The molecular-gas–star-formation relation for the z = 1–3 SFGs is near-linear, with a gas depletion timescale of about 0.7 Gyr; changes in depletion time are only a secondary effect. Since this timescale is much less than the Hubble time in all SFGs between redshifts of about 0 and 2, fresh gas must be supplied with a fairly high duty cycle over several billion years. At given z and M_star, gas fractions correlate strongly with the specific star formation rate (sSFR). The variation of sSFR between redshifts of 0 and 3 is mainly controlled by the fraction of baryonic mass that resides in cold gas.
New observations on the Galactic Center gas cloud "G2"
September 12, 2012
New observations on the gas cloud "G2" falling towards the Galactic Center confirm its highly elliptical orbit, but with updated orbital parameters. With the new data, the cloud is now expected to come even closer -- the updated pericenter distance is 2200 Schwarzschild radii -- to the super-massive black hole at the center of our galaxy. While its origin is still unclear, its apocenter is near the inner edge of the disk of young stars. This supports speculations that the cloud, which has a mass of only about three earth masses, originated as a wind of one of these stars.
In the course of this year, more observations of the cloud are planned, of course, and not only in the infrared but campaigns have been started by many groups to observe this accretion event in the whole electromagnetic spectrum. A wiki page has been set up to collect all information on "G2".
Galactic Black Hole disrupts Gas Cloud
December 14, 2011
Over the next few years, astronomers will be able to observe first-hand how the super massive black hole at the centre of our Milky Way is being fed: an international team of astronomers led by the Max Planck Institute for Extraterrestrial Physics has found a gas cloud that is falling towards the black hole in the galactic centre. While some distortion due to the huge gravitational pull of the black hole can already be seen, the gas cloud will be completely disrupted and ultimately swallowed by the black hole, resulting in largely increased X-ray emission. The observations and analysis are described in a Nature paper, published online on 14 December 2011.
For more information see
MPE Press Release.
Caught in the act: Herschel detects gigantic storms sweeping entire galaxies clean
May 09, 2011
With observations from the PACS instrument on board the ESA Herschel space observatory, an international team of scientists led by the Max Planck Institute for Extraterrestrial Physics have found gigantic storms of molecular gas gusting in the centres of many galaxies. Some of these massive outflows reach velocities of more than 1000 kilometres per second, i.e. thousands of times faster than in terrestrial hurricanes. The observations show that the more active galaxies contain stronger winds, which can blow away the entire gas reservoir in a galaxy, thereby inhibiting both further star formation and the growth of the central black hole. This finding is the first conclusive evidence for the importance of galactic winds in the evolution of galaxies.
For more information see
MPE Press Release.