Simulated sub-mm and FIR line emission from the halo of a typical star forming galaxy at z~6.5: the [CII]158micron and [OIII]88micron lines trace different regions of the circumgalactic medium (CGM)

High resolution modeling of [CII], [CI], [OIII] and CO line emission from the ISM and CGM of a star forming galaxy at z ~ 6.5 

The circumgalactic medium (CGM) is a crucial component of galaxy evolution, but thus far its physical properties are highly unconstrained. As of yet, no cosmological simulation has reached convergence when it comes to constraining the cold and dense gas fraction of the CGM. Such components are also challenging to observe, and require sub-millimeter instruments with a high sensitivity to extended, diffuse emission, like the proposed Atacama Large Aperture Sub-millimetre telescope (AtLAST). In this paper we present the first results of a state-of-the-art theoretical effort at modeling sub-mm and FIR line emission from the halo of a typical star forming galaxy at z~6.5. We find that up to 10% and 20% of the total [CII]158micron and [OIII]88micron line emissions respectively originates in the CGM. [CII] and [OIII] however trace different regions of the CGM: [CII] arises from an accreting filament and from tidal tails, while [OIII] traces a puffy halo surrounding the main disc, probably linked to SN feedback. We discuss our results in the context of current and future sub-mm observations with ALMA and AtLAST. Read the full article: Schimek et al. (2024, A&A).

Carbon monoxide (CO) and Atomic Carbon ([CI](1-0)) emission line spectra of four ULIRGs of the sample

A sensitive APEX and ALMA multi-J CO and [CI](1-0) spectral survey of 40 local (ultra-)luminous infrared galaxies

We are undertaking a multi-J CO and atomic Carbon line survey of 40 local infrared luminous galaxies (ULIRGs) with the APEX telescope, complemented by public ALMA and ACA archival data. Among the results of this work, we highlight: (i) the measurement of average higher [CI]/CO luminosity ratios in ULIRGs than found in previous, less sensitive and less uniform surveys. This result shows the limitations of previous observations that either lacked low-J CO coverage (e.g. Herschel) and/or missed a significant [CI](1-0) line flux. (ii) The discovery that the [CI](1-0) lines are narrower than the CO lines in these ULIRGs, especially in the sources that show the broadest CO line profiles. Our investigation showcases the importance of single-dish spectroscopic observations at high frequencies (500 and 800 GHz) to cover the atomic carbon lines in nearby galaxies, and motivates the development of high-frequency, high spectral resolution receivers for the future AtLAST observatory. Read the full article: Montoya Arroyave et al. (2023) (ADS link).

Left panel: Curve of growth of the CO(3-2) line emission in cid_346. Right panel: ACA CO(3-2) integrated line map

Discovery of a giant halo of molecular gas around one of the SUPER quasars at z~2

Using the ACA, we have detected a giant CO -emitting halo around cid_346, an X-ray selected z~2 SUPER quasar, where previous ALMA snapshot observations only detected a compact interstellar medium component. The ACA CO(3-2) spectrum is significantly broader than the ALMA one, the flux is ~14 times higher, and the ACA source extends out to r=200 kpc in projected size. This is the most extended molecular circumgalactic medium (CGM) reservoir that has ever been mapped. This work shows the crucial need of short baselines in high-z sub-millimeter observations, and the need for AtLAST that can enable detection of such cold CGM structures even at lower redshifts.  Read the full article here. See also ALMA science highlight in the September 2021 EU ARC Newsletter

An EU-funded Design Study for the Atacama Large Aperture Submillimeter telescope (AtLAST) is about to start

“Towards an Atacama Large Aperture Submillimeter Telescope”, in short AtLAST, is a three years long design study for a new astronomical sub-millimetre observatory.  Our project paves the way for building the largest single-dish sub-millimetre telescope in the world, which will deliver the deepest and widest maps of the sky ever obtained at these wavelengths. Read the full article here.

See also this press release by the UK Research and Innovation (UKRI).

The EU project will start in 2021. A proper website is coming soon. Meanwhile,  we are collecting emails of potential external collaborators. If you are interest in AtLAST, use this form

Extreme CN/CO ratios measured in Mrk231's molecular outflow indicating enhancement of UV radiation 

We found an exceptional boost of the CN/CO(1-0) line luminosity ratio in the massive molecular outflow of Mrk231, suggesting that the outflow material is exposed to a strong UV field. Additionally, we spectrally resolved the high-velocity HCN and HCO+(1-0) line wings into several narrow sub-structures with velocity dispersions of ~7-20 km/s, which we interpret as individual dense clumps entrained in the outflow. ADS link to the article.

Testing the blast-wave AGN feedback scenario in  a local Seyfert with an extremely powerful X-ray ultra fast outflow

Using ALMA CO(1-0) observations we ruled out the presence of a momentum-boosted molecular outflow in MCG-03-58-007, which hosts an extremely powerful X-ray ultra fast outflow. The residual emission shown in the figure is obtained by subtracting the rotation of the main disk from the ALMA data.  The favoured interpretation of the residual CO emission in MCG-03-58-007 is a biconical molecular outflow, whose momentum rate is comparable to that of the X-ray outflow. Alternatively, the residuals may trace a circumnuclear disk (CND), which however would be a factor 10-100 larger in size and mass than typical CNDs observed in local Seyferts so far.  ADS link to the article. 

The hidden circumgalactic medium that can be revealed by AtLAST 

Traditionally the circumgalactic medium (CGM) was thought to consist of warm and hot gas, but recent breakthroughs are presenting a new scenario according to which an important fraction of its mass may reside in the cold atomic and molecular phase. Such cold CGM, especially in local galaxies where its projected size is expected to be of several arcminutes, cannot be imaged by interferometers due to spatial scale filtering of large-scale structures. The only way to probe the multiphase CGM including its coldest component is through a large (e.g. 50-m class) single dish (sub-)mm telescope. This issue is illustrated in the figure, which shows the expected molecular CGM of a star forming galaxy at z = 0.02 as seen by different (sub-)mm facilities after 10 hours of observations.  Astro2020 Science white paper available at this link.

ALMA [CI](1-0) and CO line observations of NGC6240 and its massive molecular outflow

ALMA observations of the neutral Carbon line ([CI]1-0) in NGC6240 shed light on the state of the gas entrained in the massive molecular outflow, hence allowing us to constrain its extreme energetics. Furthermore, the high-resolution ALMA [CI] images surprisingly reveal that the outflow is launched between the two AGNs rather than from either of the two. ADS link to the article.

Swift X-ray telescope data hint at a binary SMBH candidate at sub-pc separation

The 123-month Swift-BAT monitoring of the nearby Seyfert galaxy MCG+11-11-032 reveals a modular behaviour with peaks and dips occurring almost every 25 months.  Under the hypothesis of an SMBH pair, such variability would imply a small sub-pc separation with an orbital velocity of ~0.06c. This value is in remarkable agreement with the energy offset of the two FeK emission lines detected in the Swift XRT spectrum of this source.

ADS link to the article.