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Register a new userSMM J04135+10277: A distant QSO-starburst system caught by ALMA
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The gas content of galaxies is a key factor for their growth, starting from star formation and black hole accretion to galaxy mergers. Thus, characterising its properties via observations of tracers like the CO emission line is of big importance in order to understand the bigger picture of galaxy evolution. We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of dust continuum, CO(5-4) and CO(8-7) line emission in the quasar--star-forming companion system SMM J04135+10277 (z=2.84). Earlier low-$J$ CO studies of this system found a huge molecular gas reservoir associated to the companion galaxy, while the quasar appeared gas-poor. Our CO observations revealed that the host galaxy of the quasar is also gas-rich, with an estimated molecular gas mass of $sim(0.7-2.3)times10^{10}$ M$_{odot}$. The CO line profiles of the companion galaxy are broad ($sim1000$ km s$^{-1}$), and show signs of rotation of a compact, massive system. In contrast to previous far-infrared observations, we resolve the continuum emission and detect both sources, with the companion galaxy dominating the dust continuum and the quasar having a $sim25%$ contribution to the total dust emission. By fitting the infrared spectral energy distribution of the sources with textsc{MR-MOOSE} and empirical templates, the infrared luminosities of the quasar and the companion are in the range of $L_{rm IR, QSO}sim(2.1-9.6)times10^{12}$ L$_{odot}$ and $L_{rm IR, Comp.}sim(2.4-24)times10^{12}$ L$_{odot}$, while the estimated star formation rates are $sim210-960$ M$_{odot}$ yr$^{-1}$ and $sim240-2400$ M$_{odot}$ yr$^{-1}$, respectively. Our results demonstrate that non-detection of low-$J$ CO transition lines in similar sources does not necessarily imply the absence of massive molecular gas reservoir but that the excitation conditions favour the excitation of high-$J$ transitions.
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(Abridged) In the last decade several massive molecular gas reservoirs were found <100 kpc distance from active galactic nuclei (AGNs), residing in gas-rich companion galaxies. The study of AGN-gas-rich companion systems opens the opportunity to determine whether the stellar mass of massive local galaxies was formed in their host after a merger event or outside of their host galaxy in a close starbursting companion and later incorporated via mergers. We study the quasar-companion galaxy system of SMM J04135+10277 (z=2.84) and investigate the expected frequency of quasar-starburst galaxy pairs at high redshift using a cosmological galaxy formation model. We use archive data and new APEX ArTeMiS data to construct and model the spectral energy distribution of SMM J04135. We also carry out a comprehensive analysis of the cosmological galaxy formation model GALFORM with the aim of characterising how typical the system of SMM J04135 is and whether quasar-star-forming galaxy pairs may constitute an important stage in galaxy evolution. The companion galaxy of SMM J04135 is a heavily dust-obscured starburst galaxy with a median star formation rate (SFR) of $700,rm{M_{odot},yr^{-1}}$, median dust mass of $5.1times 10^9,rm{M_{odot}}$ and median dust luminosity of $textrm 9.3 times 10^{12},rm{L_{odot}}$. Our simulations, performed at z=2.8, suggest that SMM J04135 is not unique. In fact, at a distance of <100 kpc, 22% of our simulated quasar sample have at least one companion galaxy of a stellar mass $>10^8, rm{M_{odot}}$, and 0.3% have at least one highly star-forming companion ($rm{SFR}>100,rm{M_{odot},yr^{-1}}$). Our results suggest that quasar-gas-rich companion galaxy systems are common phenomena in the early Universe and the high incidence of companions makes the study of such systems crucial to understand the growth and hierarchical build-up of galaxies and black holes.
We report interferometric imaging of CO(J=3-2) emission toward the z=2.846 submillimeter-selected galaxy SMM J04135+10277, using the Combined Array for Research in Millimeter-wave Astronomy (CARMA). SMM J04135+10277 was previously thought to be a gas-rich, submillimeter-selected quasar, with the highest molecular gas mass among high-z quasars reported in the literature. Our maps at ~6x improved linear resolution relative to earlier observations spatially resolve the emission on ~1.7 scales, corresponding to a (lensing-corrected) source radius of ~5.2 kpc. They also reveal that the molecular gas reservoir, and thus, likely the submillimeter emission, is not associated with the host galaxy of the quasar, but with an optically faint gas-rich galaxy at 5.2, or 41.5 kpc projected distance from the active galactic nucleus (AGN). The obscured gas-rich galaxy has a dynamical mass of M_dyn sin2(i)=5.6x10^11 M_sun, corresponding to a gas mass fraction of ~21%. Assuming a typical M_BH/M* ratio for z>2 quasars, the two galaxies in this system have an approximate mass ratio of ~1.9. Our findings suggest that this quasar-starburst galaxy pair could represent an early stage of a rare major, gas-rich/gas-poor (wet-dry) merger of two massive galaxies at z=2.8, rather than a single, gas-rich AGN host galaxy. Such systems could play an important role in the early buildup of present-day massive galaxies through a submillimeter-luminous starburst phase, and may remain hidden in larger numbers among rest-frame far-infrared-selected quasar samples at low and high redshift.
We report observations with the Atacama Large Millimetre Array (ALMA) of six submillimetre galaxies (SMGs) within 3 arcmin of the Distant Red Core (DRC) at $z=4.0$, a site of intense cluster-scale star formation, first reported by Oteo et al. (2018). We find new members of DRC in three SMG fields; in two fields, the SMGs are shown to lie along the line of sight towards DRC; one SMG is spurious. Although at first sight this rate of association is consistent with earlier predictions, associations with the bright SMGs are rarer than expected, which suggests caution when interpreting continuum over-densities. We consider the implications of all 14 confirmed DRC components passing simultaneously through an active phase of star formation. In the simplest explanation, we see only the tip of the iceberg in terms of star formation and gas available for future star formation, consistent with our remarkable finding that the majority of newly confirmed DRC galaxies are not the brightest continuum emitters in their immediate vicinity. Thus while ALMA continuum follow-up of SMGs identifies the brightest continuum emitters in each field, it does not necessarily reveal all the gas-rich galaxies. To hunt effectively for protocluster members requires wide and deep spectral-line imaging to uncover any relatively continuum-faint galaxies that are rich in atomic or molecular gas. Searching with short-baseline arrays or single-dish facilities, the true scale of the underlying gas reservoirs may be revealed.
Numerical simulations of cosmological structure formation show that the Universes most massive clusters, and the galaxies living in those clusters, assemble rapidly at early times (2.5 < z < 4). While more than twenty proto-clusters have been observed at z > 2 based on associations of 5-40 galaxies around rare sources, the observational evidence for rapid cluster formation is weak. Here we report observations of an asymmetric, filamentary structure at z = 2.47 containing seven starbursting, submillimeter-luminous galaxies and five additional AGN within a comoving volume of 15000 Mpc$^{3}$. As the expected lifetime of both the luminous AGN and starburst phase of a galaxy is ~100 Myr, we conclude that these sources were likely triggered in rapid succession by environmental factors, or, alternatively, the duration of these cosmologically rare phenomena is much longer than prior direct measurements suggest. The stellar mass already built up in the structure is $sim10^{12}M_{odot}$ and we estimate that the cluster mass will exceed that of the Coma supercluster at $z sim 0$. The filamentary structure is in line with hierarchical growth simulations which predict that the peak of cluster activity occurs rapidly at z > 2.
HH 211-mms is one of the youngest Class 0 protostellar systems in Perseus at ~ 235 pc away. We have mapped its central region at up to ~ 7 AU (0.03) resolution. A dusty disk is seen deeply embedded in a flattened envelope, with an intensity jump in dust continuum at ~ 350 GHz. It is nearly edge-on and is almost exactly perpendicular to the jet axis. It has a size of ~ 30 au along the major axis. It is geometrically thick, indicating that the (sub)millimeter light emitting grains have yet to settle to the midplane. Its inner part is expected to have transformed into a Keplerian rotating disk with a radius of ~ 10 au. A rotating disk atmosphere and a compact rotating bipolar outflow are detected in SO. The outflow fans out from the inner disk surfaces and is rotating in the same direction as the flattened envelope, and hence could trace a disk wind carrying away angular momentum from the inner disk. From the rotation of the disk atmosphere, the protostellar mass is estimated to be <~ 50 M_Jup. Together with results from the literature, our result favors a model where the disk radius grows linearly with the protostellar mass, as predicted by models of pre-stellar dense core evolution that asymptotes to an $r^{-1}$ radial profile for both the column density and angular velocity.
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