scholarly journals The non-linear infrared-radio correlation of low-z galaxies: implications for redshift evolution, a new radio SFR recipe, and how to minimize selection bias

2021 ◽  
Author(s):  
Dániel Cs Molnár ◽  
Mark T Sargent ◽  
Sarah Leslie ◽  
Benjamin Magnelli ◽  
Eva Schinnerer ◽  
...  
Keyword(s):  
Formation Rate ◽  
Wavelength Dependence ◽  
Ancillary Data ◽  
Star Forming ◽  
Distant Galaxies ◽  
New Radio ◽  
Non Linear ◽  
New Generation ◽  
First Time ◽  
Better Than

Abstract The infrared-radio correlation (IRRC) underpins many commonly used radio luminosity–star formation rate (SFR) calibrations. In preparation for the new generation of radio surveys we revisit the IRRC of low-z galaxies by (a) drawing on the best currently available IR and 1.4 GHz radio photometry, plus ancillary data over the widest possible area, and (b) carefully assessing potential systematics. We compile a catalogue of ∼9,500 z < 0.2 galaxies and derive their 1.4 GHz radio (L1.4), total IR, and monochromatic IR luminosities in up to seven bands, allowing us to parameterize the wavelength-dependence of monochromatic IRRCs from 22–500 μm. For the first time for low-z samples, we quantify how poorly matched IR and radio survey depths bias measured median IR/radio ratios, $\overline{q}_{\mathrm{TIR}}$, and discuss the level of biasing expected for low-z IRRC studies in ASKAP/MeerKAT fields. For our subset of ∼2,000 high-confidence star-forming galaxies we find a median $\overline{q}_{\mathrm{TIR}}$ of 2.54 (scatter: 0.17 dex). We show that $\overline{q}_{\mathrm{TIR}}$ correlates with L1.4, implying a non-linear IRRC with slope 1.11±0.01. Our new L1.4–SFR calibration, which incorporates this non-linearity, reproduces SFRs from panchromatic SED fits substantially better than previous IRRC-based recipes. Finally, we match the evolutionary slope of recently measured $\overline{q}_{\mathrm{TIR}}$–redshift trends without having to invoke redshift evolution of the IRRC. In this framework, the redshift evolution of $\overline{q}_{\mathrm{TIR}}$ reported at GHz frequencies in the literature is the consequence of a partial, redshift-dependent sampling of a non-linear IRRC obeyed by low-z and distant galaxies.

scholarly journals Accurate dust temperature determination in a z = 7.13 galaxy

2021 ◽  
Author(s):  
Tom J L C Bakx ◽  
Laura Sommovigo ◽  
Stefano Carniani ◽  
Andrea Ferrara ◽  
Hollis B Akins ◽  
...  
Keyword(s):  
Formation Rate ◽  
Far Infrared ◽  
Spectral Energy ◽  
Ancillary Data ◽  
Star Forming ◽  
Dust Temperature ◽  
Density Fitting ◽  
Mass Estimate ◽  
Continuum Data ◽  
First Time

Abstract We report ALMA Band 9 continuum observations of the normal, dusty star-forming galaxy A1689-zD1 at z = 7.13, resulting in a ∼4.6 σ detection at 702 GHz. For the first time these observations probe the far-infrared (FIR) spectrum shortward of the emission peak of a galaxy in the Epoch of Reionization (EoR). Together with ancillary data from earlier works, we derive the dust temperature, Td, and mass, Md, of A1689-zD1 using both traditional modified blackbody spectral energy density fitting, and a new method that relies only on the [C ii] 158 μm line and underlying continuum data. The two methods give $T_{\rm d} = (42^{+13}_{-7}, 40^{+13}_{-7}$) K, and $M_{\rm d} = (1.7^{+1.3}_{-0.7}, 2.0^{+1.8}_{-1.0})\, \times {}\, 10^{7} \, M_{\odot }$. Band 9 observations improve the accuracy of the dust temperature (mass) estimate by ∼50 per cent (6 times). The derived temperatures confirm the reported increasing Td-redshift trend between z = 0 and 8; the dust mass is consistent with a supernova origin. Although A1689-zD1 is a normal UV-selected galaxy, our results, implying that ∼85 per cent of its star formation rate is obscured, underline the non-negligible effects of dust in EoR galaxies.

scholarly journals A global correlation linking young stars, clouds, and galaxies

2018 ◽  
Vol 618 ◽  
pp. A119
Author(s):  
I. Mendigutía ◽  
C. J. Lada ◽  
R. D. Oudmaijer
Keyword(s):  
Formation Rate ◽  
Class Ii ◽  
Young Stars ◽  
Astronomical Unit ◽  
Dense Gas ◽  
Physical Reason ◽  
Star Forming ◽  
Global Correlation ◽  
Distant Galaxies ◽  
Accretion Rates

Context. The star formation rate (SFR) linearly correlates with the amount of dense gas mass (Mdg) involved in the formation of stars both for distant galaxies and clouds in our Galaxy. Similarly, the mass accretion rate (Ṁacc) and the disk mass (Mdisk) of young, Class II stars are also linearly correlated. Aims. We aim to explore the conditions under which the previous relations could be unified. Methods. Observational values of SFR, Mdg, Ṁacc, and Mdisk for a representative sample of galaxies, star forming clouds, and young stars have been compiled from the literature. Data were plotted together in order to analyze how the rate of gas transformed into stars and the mass of dense gas directly involved in this transformation relate to each other over vastly different physical systems. Results. A statistically significant correlation is found spanning ~16 orders of magnitude in each axis, but with large scatter. This probably represents one of the widest ranges of any empirical correlation known, encompassing galaxies that are several kiloparsec in size, parsec-size star-forming clouds within our Galaxy, down to young, pre-main sequence stars with astronomical unit-size protoplanetary disks. Assuming that this global correlation has an underlying physical reason, we propose a bottom-up hypothesis suggesting that a relation between Ṁacc and the total circumstellar mass surrounding Class 0/I sources (Mcs; disk + envelope) drives the correlation in clouds that host protostars and galaxies that host clouds. This hypothesis is consistent with the fact that the SFRs derived for clouds over a timescale of 2 Myr can be roughly recovered from the sum of instantaneous accretion rates of the protostars embedded within them, implying that galactic SFRs averaged over ~10–100 Myr should be constant over this period too. Moreover, the sum of the circumstellar masses directly participating in the formation of the protostellar population in a cloud likely represents a non-negligible fraction of the dense gas mass within the cloud. Conclusions. If the fraction of gas directly participating in the formation of stars is ~1–35% of the dense gas mass associated with star-forming clouds and galaxies, then the global correlation for all scales has a near unity slope and an intercept consistent with the (proto-)stellar accretion timescale, Mcs/ Ṁacc. Therefore, an additional critical test of our hypothesis is that the Ṁacc−Mdisk correlation for Class II stars should also be observed between Ṁacc and Mcs for Class 0/I sources with similar slope and intercept.

scholarly journals The infrared-radio correlation of star-forming galaxies is strongly M⋆-dependent but nearly redshift-invariant since z ∼ 4

2021 ◽  
Vol 647 ◽  
pp. A123
Author(s):  
I. Delvecchio ◽  
E. Daddi ◽  
M. T. Sargent ◽  
M. J. Jarvis ◽  
D. Elbaz ◽  
...  
Keyword(s):  
Star Formation Rate ◽  
High Redshift ◽  
Formation Rate ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Massive Galaxies ◽  
Star Forming ◽  
The Past ◽  
First Time ◽  
Best Fit

Over the past decade, several works have used the ratio between total (rest 8−1000 μm) infrared and radio (rest 1.4 GHz) luminosity in star-forming galaxies (qIR), often referred to as the infrared-radio correlation (IRRC), to calibrate the radio emission as a star formation rate (SFR) indicator. Previous studies constrained the evolution of qIR with redshift, finding a mild but significant decline that is yet to be understood. Here, for the first time, we calibrate qIR as a function of both stellar mass (M⋆) and redshift, starting from an M⋆-selected sample of > 400 000 star-forming galaxies in the COSMOS field, identified via (NUV − r)/(r − J) colours, at redshifts of 0.1 < z < 4.5. Within each (M⋆,z) bin, we stacked the deepest available infrared/sub-mm and radio images. We fit the stacked IR spectral energy distributions with typical star-forming galaxy and IR-AGN templates. We then carefully removed the radio AGN candidates via a recursive approach. We find that the IRRC evolves primarily with M⋆, with more massive galaxies displaying a systematically lower qIR. A secondary, weaker dependence on redshift is also observed. The best-fit analytical expression is the following: qIR(M⋆, z) = (2.646 ± 0.024) × (1 + z)( − 0.023 ± 0.008)–(0.148 ± 0.013) × (log M⋆/M⊙ − 10). Adding the UV dust-uncorrected contribution to the IR as a proxy for the total SFR would further steepen the qIR dependence on M⋆. We interpret the apparent redshift decline reported in previous works as due to low-M⋆ galaxies being progressively under-represented at high redshift, as a consequence of binning only in redshift and using either infrared or radio-detected samples. The lower IR/radio ratios seen in more massive galaxies are well described by their higher observed SFR surface densities. Our findings highlight the fact that using radio-synchrotron emission as a proxy for SFR requires novel M⋆-dependent recipes that will enable us to convert detections from future ultra-deep radio surveys into accurate SFR measurements down to low-M⋆ galaxies with low SFR.

scholarly journals The rapid evolution of dust content in galaxies over the last five billion years

2012 ◽  
Vol 8 (S292) ◽  
pp. 275-278
Author(s):  
H. L. Gomez ◽  
L. Dunne ◽  
D. J. B. Smith ◽  
E. da Cunha
Keyword(s):  
Formation Rate ◽  
Rapid Evolution ◽  
Mass Function ◽  
Initial Mass Function ◽  
Stellar Atmospheres ◽  
Dust Content ◽  
Star Forming ◽  
First Time ◽  
Stellar Source ◽  
Science Demonstration

AbstractThe Herschel-ATLAS (H-ATLAS) will provide an unrivalled sample of galaxies, probing the normal star-forming submillimetre population of galaxies for the first time. Here, we exploit the Science Demonstration Phase (SDP) data to model the evolution of the interstellar content of galaxies in recent history. The most massive H-ATLAS galaxies show a large increase in the dust content five billion years ago compared to the present epoch. These observations are difficult to explain using standard dust models, one possibility could be contributions from a non-stellar source of dust e.g. grain growth in dense clouds; this would imply that less than 10% of dust would be condensed in stellar atmospheres. Alternatively, an initial mass function which becomes top heavy at high star formation rate densities could also explain this discrepancy.

scholarly journals PhotoWeb redshift: boosting photometric redshift accuracy with large spectroscopic surveys

2020 ◽  
Vol 636 ◽  
pp. A90 ◽  
Author(s):  
M. Shuntov ◽  
J. Pasquet ◽  
S. Arnouts ◽  
O. Ilbert ◽  
M. Treyer ◽  
...  
Keyword(s):  
Large Scale ◽  
Distribution Functions ◽  
Distance Measurements ◽  
Photometric Redshifts ◽  
Star Forming ◽  
Photometric Redshift ◽  
Probability Distribution Functions ◽  
Galaxy Sample ◽  
New Generation ◽  
Better Than

Improving distance measurements in large imaging surveys is a major challenge to better reveal the distribution of galaxies on a large scale and to link galaxy properties with their environments. As recently shown, photometric redshifts can be efficiently combined with the cosmic web extracted from overlapping spectroscopic surveys to improve their accuracy. In this paper we apply a similar method using a new generation of photometric redshifts based on a convolution neural network (CNN). The CNN is trained on the SDSS images with the main galaxy sample (SDSS-MGS, r ≤ 17.8) and the GAMA spectroscopic redshifts up to r ∼ 19.8. The mapping of the cosmic web is obtained with 680 000 spectroscopic redshifts from the MGS and BOSS surveys. The redshift probability distribution functions (PDF), which are well calibrated (unbiased and narrow, ≤120 Mpc), intercept a few cosmic web structures along the line of sight. Combining these PDFs with the density field distribution provides new photometric redshifts, zweb, whose accuracy is improved by a factor of two (i.e., σ ∼ 0.004(1 + z)) for galaxies with r ≤ 17.8. For half of them, the distance accuracy is better than 10 cMpc. The narrower the original PDF, the larger the boost in accuracy. No gain is observed for original PDFs wider than 0.03. The final zweb PDFs also appear well calibrated. The method performs slightly better for passive galaxies than star-forming ones, and for galaxies in massive groups since these populations better trace the underlying large-scale structure. Reducing the spectroscopic sampling by a factor of 8 still improves the photometric redshift accuracy by 25%. Finally, extending the method to galaxies fainter than the MGS limit still improves the redshift estimates for 70% of the galaxies, with a gain in accuracy of 20% at low z where the resolution of the cosmic web is the highest. As two competing factors contribute to the performance of the method, the photometric redshift accuracy and the resolution of the cosmic web, the benefit of combining cosmological imaging surveys with spectroscopic surveys at higher redshift remains to be evaluated.

scholarly journals Star formation in CALIFA early-type galaxies: a matter of discs

2019 ◽  
Vol 488 (1) ◽  
pp. L80-L84 ◽  
Author(s):  
J Méndez-Abreu ◽  
S F Sánchez ◽  
A de Lorenzo-Cáceres
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Formation Rate ◽  
Molecular Gas ◽  
Early Type ◽  
Star Forming ◽  
Integral Field Spectroscopy ◽  
The Galaxy ◽  
First Time ◽  
Integral Field

ABSTRACT The star formation main sequence (SFMS) is a tight relation between the galaxy star formation rate (SFR) and its total stellar mass (M⋆). Early-type galaxies (ETGs) are often considered as low-SFR outliers of this relation. We study, for the first time, the separated distribution in the SFR versus M⋆ of bulges and discs of 49 ETGs from the CALIFA survey. This is achieved using c2d, a new code to perform spectrophotometric decompositions of integral field spectroscopy data cubes. Our results reflect that: (i) star formation always occurs in the disc component and not in bulges; (ii) star-forming discs in our ETGs are compatible with the SFMS defined by star-forming galaxies at z ∼ 0; (iii) the star formation is not confined to the outskirts of discs, but it is present at all radii (even where the bulge dominates the light); (iv) for a given mass, bulges exhibit lower sSFR than discs at all radii; and (v) we do not find a deficit of molecular gas in bulges with respect to discs for a given mass in our ETGs. We speculate our results favour a morphological quenching scenario for ETGs.

scholarly journals Extremely deep 150 MHz source counts from the LoTSS Deep Fields

2021 ◽  
Vol 648 ◽  
pp. A5 ◽  
Author(s):  
S. Mandal ◽  
I. Prandoni ◽  
M. J. Hardcastle ◽  
T. W. Shimwell ◽  
H. T. Intema ◽  
...  
Keyword(s):  
Low Frequency ◽  
Careful Analysis ◽  
Star Forming ◽  
Sky Survey ◽  
Deep Fields ◽  
Galaxy Population ◽  
Calibration Techniques ◽  
New Generation ◽  
Intermediate Redshift ◽  
First Time

With the advent of new generation low-frequency telescopes, such as the LOw Frequency ARray (LOFAR), and improved calibration techniques, we have now started to unveil the subgigahertz radio sky with unprecedented depth and sensitivity. The LOFAR Two Meter Sky Survey (LoTSS) is an ongoing project in which the whole northern radio sky will be observed at 150 MHz with a sensitivity better than 100 μJy beam−1 at a resolution of 6′′. Additionally, deeper observations are planned to cover smaller areas with higher sensitivity. The Lockman Hole, the Boötes, and the Elais-N1 regions are among the most well known northern extra-galactic fields and the deepest of the LoTSS Deep Fields so far. We exploited these deep observations to derive the deepest radio source counts at 150 MHz to date. Our counts are in broad agreement with those from the literature and show the well known upturn at ≤1 mJy, mainly associated with the emergence of the star-forming galaxy population. More interestingly, our counts show, for the first time a very pronounced drop around S ~ 2 mJy, which results in a prominent “bump” at sub-mJy flux densities. Such a feature was not observed in previous counts’ determinations (neither at 150 MHz nor at a higher frequency). While sample variance can play a role in explaining the observed discrepancies, we believe this is mostly the result of a careful analysis aimed at deblending confused sources and removing spurious sources and artifacts from the radio catalogs. This “drop and bump” feature cannot be reproduced by any of the existing state-of-the-art evolutionary models, and it appears to be associated with a deficiency of active galactic nuclei (AGN) at an intermediate redshift (1 < z < 2) and an excess of low-redshift (z < 1) galaxies and/or AGN.

scholarly journals Environmental effects on star formation main sequence in the COSMOS field

2019 ◽  
Vol 15 (S356) ◽  
pp. 339-341
Author(s):  
Solohery M. Randriamampandry ◽  
Mattia Vaccari ◽  
Kelley M. Hess
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Main Sequence ◽  
Formation Rate ◽  
Galactic Nuclei ◽  
Star Forming ◽  
Consensus Region ◽  
Galaxy Environment ◽  
First Time ◽  
The Relationship

AbstractWe investigate the relationship between environment and star formation main sequence (the relationship between stellar mass and star formation rate) to shed new light on the effects of the environments on star-forming galaxies. We use the large VLA-COSMOS 3 GHz catalogue that consist of star-forming galaxies (SFGs) and active galactic nuclei (AGN) in three different environments (field, filament, cluster) and for different galaxy types. We examine for the first time a comparative analysis for the distribution of SFGs with respect to the star formation main sequence (MS) consensus region from the literature, taking into account galaxy environment and using radio selected sample at 0.1 ≤ z ≤ 1.2 drawn from one of the deepest COSMOS radio surveys. We find that, as observed previously, SFRs increase with redshift independent on the environments. Furthermore, we observe that SFRs versus M* relation is flat in all cases, irrespective of the redshift and environments.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

Recent developments in low-voltage SEM of polymers

1993 ◽  
Vol 51 ◽  
pp. 866-867
Author(s):  
S.J. Krause ◽  
W.W. Adams
Keyword(s):  
Low Voltage ◽  
Chromatic Aberration ◽  
Thermal Electron ◽  
Analytical Technique ◽  
Recent Developments ◽  
Beam Currents ◽  
New Generation ◽  
First Time ◽  
Voltage Scanning ◽  
Beam Damage

Over the past decade low voltage scanning electron microscopy (LVSEM) of polymers has evolved from an interesting curiosity to a powerful analytical technique. This development has been driven by improved instrumentation and in particular, reliable field emission gun (FEG) SEMs. The usefulness of LVSEM has also grown because of an improved theoretical and experimental understanding of sample-beam interactions and by advances in sample preparation and operating techniques. This paper will review progress in polymer LVSEM and present recent results and developments in the field.In the early 1980s a new generation of SEMs produced beam currents that were sufficient to allow imaging at low voltages from 5keV to 0.5 keV. Thus, for the first time, it became possible to routinely image uncoated polymers at voltages below their negative charging threshold, the "second crossover", E2 (Fig. 1). LVSEM also improved contrast and reduced beam damage in sputter metal coated polymers. Unfortunately, resolution was limited to a few tenths of a micron due to the low brightness and chromatic aberration of thermal electron emission sources.

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