Megaparsec-scale structure around the protocluster core SPT2349–56 at z = 4.3

ABSTRACT We present an extensive ALMA spectroscopic follow-up programme of the $z\, {=}\, 4.3$ structure SPT2349–56, one of the most actively star-forming protocluster cores known, to identify additional members using their [C ii] 158 μm and CO(4–3) lines. In addition to robustly detecting the 14 previously published galaxies in this structure, we identify a further 15 associated galaxies at $z\, {=}\, 4.3$, resolving 55$\, {\pm }\,$5 per cent of the 870 μm flux density at 0.5 arcsec resolution compared to 21 arcsec single-dish data. These galaxies are distributed into a central core containing 23 galaxies extending out to 300 kpc in diameter, and a northern extension, offset from the core by 400 kpc, containing three galaxies. We discovered three additional galaxies in a red Herschel-SPIRE source 1.5 Mpc from the main structure, suggesting the existence of many other sources at the same redshift as SPT2349–56 that are not yet detected in the limited coverage of our data. An analysis of the velocity distribution of the central galaxies indicates that this region may be virialized with a mass of (9$\pm 5)\, {\times }\, 10^{12}$ M⊙, while the two offset galaxy groups are about 30 and 60 per cent less massive and show significant velocity offsets from the central group. We calculate the [C ii] and far-infrared number counts, and find evidence for a break in the [C ii] luminosity function. We estimate the average SFR density within the region of SPT2349–56 containing single-dish emission (a proper diameter of 720 kpc), assuming spherical symmetry, to be roughly 4$\, {\times }\, 10^4$ M⊙ yr−1 Mpc−3; this may be an order of magnitude greater than the most extreme examples seen in simulations.

Download Full-text

Multi-wavelength de-blended Herschel view of the statistical properties of dusty star-forming galaxies across cosmic time

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834093 ◽

2019 ◽

Vol 624 ◽

pp. A98 ◽

Cited By ~ 4

Author(s):

L. Wang ◽

W. J. Pearson ◽

W. Cowley ◽

J. W. Trayford ◽

M. Béthermin ◽

...

Keyword(s):

Star Formation ◽

Dynamic Range ◽

Transition Period ◽

Formation Rate ◽

Cosmic Time ◽

Far Infrared ◽

Statistical Properties ◽

Star Forming ◽

Multi Wavelength ◽

Number Counts

Aims. We study the statistical properties of dusty star-forming galaxies across cosmic time, such as their number counts, luminosity functions (LF), and the dust-obscured star formation rate density (SFRD). Methods. We used the most recent de-blended Herschel catalogue in the COSMOS field to measure the number counts and LFs at far-infrared (FIR) and sub-millimetre (sub-mm) wavelengths. The de-blended catalogue was generated by combining the Bayesian source extraction tool XID+ and an informative prior derived from the associated deep multi-wavelength photometric data. Results. Through our de-confusion technique and based on the deep multi-wavelength photometric information, we are able to achieve more accurate measurements while at the same time probing roughly ten times below the Herschel confusion limit. Our number counts at 250 μm agree well with previous Herschel studies. However, our counts at 350 and 500 μm are below previous Herschel results because previous Herschel studies suffered from source confusion and blending issues. Our number counts at 450 and 870 μm show excellent agreement with previous determinations derived from single-dish and interferometric observations. Our measurements of the LF at 250 μm and the total IR LF agree well with previous results in the overlapping redshift and luminosity range. The increased dynamic range of our measurements allows us to better measure the faint-end of the LF and measure the dust-obscured SFRD out to z ∼ 6. We find that the fraction of obscured star formation activity is at its highest (>80%) around z ∼ 1. We do not find a shift of balance between z ∼ 3 and z ∼ 4 in the SFRD from being dominated by unobscured star formation at higher redshift to obscured star formation at lower redshift. However, we do find 3 < z < 4 to be an interesting transition period as the portion of the total SFRD that is obscured by dust is significantly lower at higher redshifts.

Download Full-text

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). VIII. A less biased view of the early co-evolution of black holes and host galaxies

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psz096 ◽

2019 ◽

Vol 71 (6) ◽

Cited By ~ 10

Author(s):

Takuma Izumi ◽

Masafusa Onoue ◽

Yoshiki Matsuoka ◽

Tohru Nagao ◽

Michael A Strauss ◽

...

Keyword(s):

Black Holes ◽

Far Infrared ◽

Supermassive Black Holes ◽

Host Galaxies ◽

Star Forming ◽

Wide Range ◽

The Galaxy ◽

Order Of Magnitude ◽

Local Relation ◽

Almost All

Abstract We present ALMA [C ii] line and far-infrared (FIR) continuum observations of three $z \gt 6$ low-luminosity quasars ($M_{\rm 1450} \gt -25$ mag) discovered by our Subaru Hyper Suprime-Cam (HSC) survey. The [C ii] line was detected in all three targets with luminosities of $(2.4\mbox{--}9.5) \times 10^8\, L_{\odot }$, about one order of magnitude smaller than optically luminous ($M_{\rm 1450} \lesssim -25$ mag) quasars. The FIR continuum luminosities range from $\lt 9 \times 10^{10}\, L_{\odot }$ (3 $\sigma$ limit) to ${\sim } 2 \times 10^{12}\, L_{\odot }$, indicating a wide range in star formation rates in these galaxies. Most of the HSC quasars studied thus far show [C ii]/ FIR luminosity ratios similar to local star-forming galaxies. Using the [C ii]-based dynamical mass ($M_{\rm dyn}$) as a surrogate for bulge stellar mass ($M_{\rm\, bulge}$), we find that a significant fraction of low-luminosity quasars are located on or even below the local $M_{\rm\, BH}$–$M_{\rm\, bulge}$ relation, particularly at the massive end of the galaxy mass distribution. In contrast, previous studies of optically luminous quasars have found that black holes are overmassive relative to the local relation. Given the low luminosities of our targets, we are exploring the nature of the early co-evolution of supermassive black holes and their hosts in a less biased way. Almost all of the quasars presented in this work are growing their black hole mass at a much higher pace at $z \sim 6$ than the parallel growth model, in which supermassive black holes and their hosts grow simultaneously to match the local $M_{\rm\, BH}$–$M_{\rm\, bulge}$ relation at all redshifts. As the low-luminosity quasars appear to realize the local co-evolutionary relation even at $z \sim 6$, they should have experienced vigorous starbursts prior to the currently observed quasar phase to catch up with the relation.

Download Full-text

SCUBA-2 overdensities associated with candidate protoclusters selected from Planck data

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1096 ◽

2020 ◽

Vol 494 (4) ◽

pp. 5985-5991

Author(s):

T Cheng ◽

D L Clements ◽

J Greenslade ◽

J Cairns ◽

P Andreani ◽

...

Keyword(s):

Star Formation ◽

Star Formation Rate ◽

Formation Rate ◽

Intermediate Level ◽

Planck Data ◽

Star Forming ◽

Compact Source ◽

Number Counts ◽

Compact Sources

ABSTRACT We measure the 850-μm source densities of 46 candidate protoclusters selected from the Planck high-z catalogue (PHz) and the Planck Catalogue of Compact Sources (PCCS) that were followed up with Herschel-SPIRE and SCUBA-2. This paper aims to search for overdensities of 850-μm sources in order to select the fields that are most likely to be genuine protoclusters. Of the 46 candidate protoclusters, 25 have significant overdensities (>5 times the field counts), 11 have intermediate overdensities (3–5 times the field counts), and 10 have no overdensity (<3 times the field counts) of 850-μm sources. We find that the enhanced number densities are unlikely to be the result of sample variance. Compared with the number counts of another sample selected from Planck’s compact source catalogues, this [PHz + PCCS]-selected sample has a higher fraction of candidate protoclusters with significant overdensities, though both samples show overdensities of 850-μm sources above intermediate level. Based on the estimated star formation rate densities (SFRDs), we suggest that both samples can efficiently select protoclusters with starbursting galaxies near the redshift at which the global field SFRD peaks (2 < z < 3). Based on the confirmation of overdensities found here, future follow-up observations on other PHz targets may greatly increase the number of genuine dusty star-forming galaxy-rich clusters/protoclusters.

Download Full-text

A centrally concentrated sub-solar-mass starless core in the Taurus L1495 filamentary complex

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psz051 ◽

2019 ◽

Vol 71 (4) ◽

Cited By ~ 3

Author(s):

Kazuki Tokuda ◽

Kengo Tachihara ◽

Kazuya Saigo ◽

Phillipe André ◽

Yosuke Miyamoto ◽

...

Keyword(s):

Star Formation ◽

Initial Conditions ◽

Volume Density ◽

Mass Star ◽

Brown Dwarf ◽

Solar Mass ◽

Star Forming ◽

The Core ◽

Order Of Magnitude ◽

Low Mass

Abstract The formation scenario of brown dwarfs is still unclear because observational studies to investigate its initial condition are quite limited. Our systematic survey of nearby low-mass star-forming regions using the Atacama Compact Array (aka the Morita array) and the IRAM 30-m telescope in 1.2 mm continuum has identified a centrally concentrated starless condensation with a central H2 volume density of ∼106 cm−3, MC5-N, connected to a narrow (width ∼0.03 pc) filamentary cloud in the Taurus L1495 region. The mass of the core is $\sim {0.2\!-\!0.4}\, M_{\odot }$, which is an order of magnitude smaller than typical low-mass pre-stellar cores. Taking into account a typical core to star formation efficiency for pre-stellar cores (∼20%–40%) in nearby molecular clouds, brown dwarf(s) or very low-mass star(s) may be going to be formed in this core. We have found possible substructures at the high-density portion of the core, although much higher angular resolution observation is needed to clearly confirm them. The subsequent N2H+ and N2D+ observations using the Nobeyama 45-m telescope have confirmed the high-deuterium fractionation (∼30%). These dynamically and chemically evolved features indicate that this core is on the verge of proto-brown dwarf or very low-mass star formation and is an ideal source to investigate the initial conditions of such low-mass objects via gravitational collapse and/or fragmentation of the filamentary cloud complex.

Download Full-text

The brightest galaxies in the dark ages: Galaxies’ dust continuum emission out to the reionization era

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320001350 ◽

2019 ◽

Vol 15 (S352) ◽

pp. 349-349

Author(s):

Caitlin Casey

Keyword(s):

Star Formation ◽

Early Universe ◽

Luminosity Function ◽

Formation Rate ◽

Continuum Emission ◽

Spectral Energy ◽

Universe Model ◽

Star Forming ◽

Number Counts ◽

Galaxy Luminosity Function

AbstractThough half of cosmic starlight is absorbed by dust and reradiated at long wavelengths (3μ m – 3 mm), constraints on the infrared through millimeter galaxy luminosity function (the ‘IRLF’) are poor in comparison to the rest-frame ultraviolet and optical galaxy luminosity function, particularly at z ⩾ 2.5. Here we present a backward evolution model for interpreting number counts, redshift distributions, and cross-band flux density correlations in the infrared and submillimeter sky, from 70μm – 2 mm, using a model for the IRLF out to the epoch of reionization. Mock submillimeter maps are generated by injecting sources according to the prescribed IRLF and flux densities drawn from model spectral energy distributions that mirror the distribution of SEDs observed in 0 < z 0 < 5 dusty star-forming galaxies (DSFGs). We explore two extreme hypothetical case-studies: a dust-poor early Universe model, where DSFGs contribute negligibly (< 10%) to the integrated star-formation rate density at z > 4, and an alternate dust-rich early Universe model, where DSFGs dominate > 90% of z > 4 star-formation. We find that current submm/mm datasets do not clearly rule out either of these extreme models. We suggest that future surveys at 2 mm – both from ALMA and single-dish facilities – will be crucial to measuring the IRLF beyond z > 4.

Download Full-text

X-ray emission from hot gas in galaxy groups and clusters in simba

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2394 ◽

2020 ◽

Vol 498 (3) ◽

pp. 3061-3076

Author(s):

Dylan Robson ◽

Romeel Davé

Keyword(s):

Galaxy Formation ◽

Self Similarity ◽

Dominant Form ◽

Density Profiles ◽

X Ray ◽

Star Forming ◽

Galaxy Groups ◽

The Core ◽

Self Similar ◽

Electron Density Profiles

ABSTRACT We examine X-ray scaling relations for massive haloes ($M_{500}\gt 10^{12.3}\, \mathrm{M}_\odot$) in the simba galaxy formation simulation. The X-ray luminosity, LX versus M500 has power-law slopes ${\approx }\frac{5}{3}$ and ${\approx }\frac{8}{3}$ above and below $10^{13.5} \, \mathrm{M}_{\odot }$, deviating from the self-similarity increasingly to low masses. TX − M500 is self-similar above this mass, and slightly shallower below it. Comparing simba to observed TX scalings, we find that LX, LX-weighted [Fe/H], and entropies at 0.1R200 (S0.1) and R500 (S500) all match reasonably well. S500 − TX is consistent with self-similar expectations, but S0.1 − TX is shallower at lower TX, suggesting the dominant form of heating moves from gravitational shocks in the outskirts to non-gravitational feedback in the cores of smaller groups. simba matches observations of LX versus central galaxy stellar mass M*, predicting the additional trend that star-forming galaxies have higher LX(M*). Electron density profiles for $M_{500}\gt 10^{14}\, \mathrm{M}_\odot$ haloes show a ∼0.1R200 core, but the core is larger at lower masses. TX are reasonably matched to observations, but entropy profiles are too flat versus observations for intermediate-mass haloes, with Score ≈ 200–400 keV cm2. simba’s [Fe/H] profile matches observations in the core but overenriches larger radii. We demonstrate that Simba’s bipolar jet AGN feedback is most responsible for increasingly evacuating lower-mass haloes, but the profile comparisons suggest this may be too drastic in the inner regions.

Download Full-text

Proximate molecular quasar absorbers

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935371 ◽

2019 ◽

Vol 627 ◽

pp. A32 ◽

Cited By ~ 2

Author(s):

P. Noterdaeme ◽

S. Balashev ◽

J.-K. Krogager ◽

R. Srianand ◽

H. Fathivavsari ◽

...

Keyword(s):

Control Sample ◽

Neutral Hydrogen ◽

Sloan Digital Sky Survey ◽

Metal Species ◽

Physical Conditions ◽

The Core ◽

Sky Survey ◽

Large Spread ◽

Order Of Magnitude

We present results from a search for strong H2 absorption systems proximate to quasars (zabs ≈ zem) in the Sloan Digital Sky Survey (SDSS) Data Release 14. The search is based on the Lyman-Werner band signature of damped H2 absorption lines without any prior on the associated metal or neutral hydrogen content. This has resulted in the detection of 81 systems with N(H2) ∼ 1019 − 1020 cm−2 located within a few thousand km s−1 from the quasar. Compared to a control sample of intervening systems, this implies an excess of proximate H2 systems by about a factor of 4 to 5. The incidence of H2 systems increases steeply with decreasing relative velocity, reaching an order of magnitude higher than expected from intervening statistics at Δv < 1000 km s−1. The most striking feature of the proximate systems compared to the intervening ones is the presence of Ly − α emission in the core of the associated damped H I absorption line in about half of the sample. This puts constraints on the relative projected sizes of the absorbing clouds to those of the quasar line emitting regions. Using the SDSS spectra, we estimate the H I, metal and dust content of the systems, which are found to have typical metallicities of one tenth Solar, albeit with a large spread among individual systems. We observe trends between the fraction of leaking Ly − α emission and the relative absorber-quasar velocity as well as with the excitation of several metal species, similar to what has been seen in metal-selected proximate DLAs. With the help of theoretical H I-H2 transition relations, we show that the presence of H2 helps to break the degeneracy between density and strength of the UV field as main sources of excitation and hence provides unique constraints on the possible origin and location of the absorbing clouds. We suggest that most of these systems originate from galaxies in the quasar group, although a small fraction of them could be located in the quasar host as well. We conclude that follow-up observations are still required to investigate the chemical and physical conditions in individual clouds and to assess the importance of AGN feedback for the formation and survival of H2 clouds.

Download Full-text

First detection of NHD and ND2 in the interstellar medium

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038490 ◽

2020 ◽

Vol 641 ◽

pp. A153

Author(s):

M. Melosso ◽

L. Bizzocchi ◽

O. Sipilä ◽

B. M. Giuliano ◽

L. Dore ◽

...

Keyword(s):

Interstellar Medium ◽

Column Density ◽

Molecular Spectroscopy ◽

Far Infrared ◽

Chemical Model ◽

Star Forming ◽

Star Forming Regions ◽

Submillimeter Wavelengths ◽

Order Of Magnitude ◽

Low Mass

Context. Deuterium fractionation processes in the interstellar medium (ISM) have been shown to be highly efficient in the family of nitrogen hydrides. To date, observations have been limited to ammonia (NH2D, NHD2, ND3) and imidogen radical (ND) isotopologues. Aims. We want to explore the high-frequency windows offered by the Herschel Space Observatory to search for deuterated forms of the amidogen radical NH2 and to compare the observations against the predictions of our comprehensive gas-grain chemical model. Methods. Making use of the new molecular spectroscopy data recently obtained at high frequencies for NHD and ND2, we searched for both isotopologues in the spectral survey toward the Class 0 protostar IRAS 16293-2422, a source in which NH3, NH, and their deuterated variants have previously been detected. We used the observations carried out with HIFI (Heterodyne Instrument for the Far-Infrared) in the framework of the key program “Chemical Herschel surveys of star forming regions” (CHESS). Results. We report the first detection of interstellar NHD and ND2. Both species are observed in absorption against the continuum of the protostar. From the analysis of their hyperfine structure, accurate excitation temperature and column density values are determined. The latter were combined with the column density of the parent species NH2 to derive the deuterium fractionation in amidogen. We find a high deuteration level of amidogen radical in IRAS 16293-2422, with a deuterium enhancement about one order of magnitude higher than that predicted by earlier astrochemical models. Such a high enhancement can only be reproduced by a gas-grain chemical model if the pre-stellar phase preceding the formation of the protostellar system has a long duration: on the order of one million years. Conclusions. The amidogen D/H ratio measured in the low-mass protostar IRAS 16293-2422 is comparable to that derived for the related species imidogen and much higher than that observed for ammonia. Additional observations of these species will provide more insights into the mechanism of ammonia formation and deuteration in the ISM. Finally, we indicate the current possibilities to further explore these species at submillimeter wavelengths.

Download Full-text

Galaxy Evolution in the Infrared: Number Counts and Cosmic Infrared Background

Symposium - International Astronomical Union ◽

10.1017/s007418090022620x ◽

2001 ◽

Vol 204 ◽

pp. 303-303

Author(s):

T. T. Takeuchi ◽

H. Hirashita ◽

T. T. Ishii ◽

K. Yoshikawa

Keyword(s):

Galaxy Evolution ◽

Evolutionary History ◽

Rapid Evolution ◽

Far Infrared ◽

The Galaxy ◽

Evolutionary Phase ◽

Infrared Background ◽

Order Of Magnitude ◽

Cosmic Infrared Background ◽

Number Counts

Recently reported infrared galaxy number counts and cosmic infrared background (CIRB) measures all suggest that galaxies have experienced a strong evolutionary phase. We statistically estimated the galaxy evolution history from these data. We treated the evolution of galaxy luminosity as a stepwise nonparametric form, in order to explore the most suitable evolutionary history which satisfies the constraint from the CIRB. We found that an order of magnitude increase of the far infrared luminosity at redshift z = 0.75 - 1.0 was necessary to reproduce the very high CIRB intensity at ~ 150 μm reported by Hauser et al. (1998). We note that too large an evolutionary factor at high z overpredicts the CIRB intensity around 1 mm. The evolutionary history also satisfies the constraints from galaxy number counts obtained by IRAS, ISO and SCUBA. The rapid evolution of the IR luminosity density required from the CIRB well reproduces the very steep slope of galaxy number counts obtained by ISO. Based on this result and the evolution of optical luminosity density, we quantitatively discuss the contribution of starburst galaxies. In addition, we present the performance of the Japanese IRIS galaxy survey.

Download Full-text