scholarly journals The Environmental Dependence of Gas Properties in Dense Cores of a Protocluster at z ∼ 2.5 Revealed with ALMA

2022 ◽  
Vol 924 (2) ◽  
pp. 74
Author(s):  
Kohei Aoyama ◽  
Tadayuki Kodama ◽  
Tomoko L. Suzuki ◽  
Ken-ichi Tadaki ◽  
Rhythm Shimakawa ◽  
...  
Keyword(s):  
Star Formation ◽  
Interstellar Dust ◽  
Formation Rate ◽  
Stellar Mass ◽  
Continuum Emission ◽  
Star Forming ◽  
Dense Cores ◽  
Mass Ratios ◽  
Mass Fractions ◽  
Gas Properties

Abstract In a protocluster USS1558-003 at z = 2.53, galaxies in the dense cores show systematically elevated star-forming activity compared to those in less dense regions. To understand its origin, we look into the gas properties of the galaxies in the dense cores by conducting deep 1.1 mm observations with the Atacama Large Millimeter/submillimeter Array. We detect interstellar dust continuum emission from 12 member galaxies and estimate their molecular gas masses. Comparing these gas masses with our previous measurements from the CO(3–2) line, we infer that the latter might be overestimated. We find that the gas to stellar mass ratios of the galaxies in the dense cores tend to be higher (at M * ∼ 1010 M ⊙ where we see the enhanced star-forming activity), suggesting that such large gas masses can sustain their high star-forming activity. However, if we compare the gas properties of these protocluster galaxies with the gas scaling relations constructed for field galaxies at a similar cosmic epoch, we find no significant environmental difference at the same stellar mass and star formation rate. Although both gas mass ratios and star-forming activity are enhanced in the majority of member galaxies, they appear to follow the same scaling relation as field galaxies. Our results are consistent with the scenario in which the cold gas is efficiently supplied to protocluster cores and to galaxies therein along surrounding filamentary structures, which leads to the high gas mass fractions and thus the elevated star formation activity, but without changing the star formation law.

scholarly journals Radio continuum size evolution of star-forming galaxies over 0.35 < z < 2.25

2019 ◽  
Vol 625 ◽  
pp. A114 ◽  
Author(s):  
E. F. Jiménez-Andrade ◽  
B. Magnelli ◽  
A. Karim ◽  
G. Zamorani ◽  
M. Bondi ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Gaussian Model ◽  
Cosmic Time ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Selection Function ◽  
Star Forming ◽  
Size Evolution ◽  
Galaxy Population

To better constrain the physical mechanisms driving star formation, we present the first systematic study of the radio continuum size evolution of star-forming galaxies (SFGs) over the redshift range 0.35 <  z <  2.25. We use the VLA COSMOS 3 GHz map (noise rms = 2.3 μJy beam−1, θbeam = 0.75 arcsec) to construct a mass-complete sample of 3184 radio-selected SFGs that reside on and above the main sequence (MS) of SFGs. We constrain the overall extent of star formation activity in galaxies by applying a 2D Gaussian model to their radio continuum emission. Extensive Monte Carlo simulations are used to validate the robustness of our measurements and characterize the selection function. We find no clear dependence between the radio size and stellar mass, M⋆, of SFGs with 10.5 ≲ log(M⋆/M⊙) ≲ 11.5. Our analysis suggests that MS galaxies are preferentially extended, while SFGs above the MS are always compact. The median effective radius of SFGs on (above) the MS of Reff = 1.5 ± 0.2 (1.0 ± 0.2) kpc remains nearly constant with cosmic time; a parametrization of the form Reff ∝ (1 + z)α yields a shallow slope of only α = −0.26 ± 0.08 (0.12 ± 0.14) for SFGs on (above) the MS. The size of the stellar component of galaxies is larger than the extent of the radio continuum emission by a factor ∼2 (1.3) at z = 0.5 (2), indicating star formation is enhanced at small radii. The galactic-averaged star formation rate surface density (ΣSFR) scales with the distance to the MS, except for a fraction of MS galaxies (≲10%) that harbor starburst-like ΣSFR. These “hidden” starbursts might have experienced a compaction phase due to disk instability and/or a merger-driven burst of star formation, which may or may not significantly offset a galaxy from the MS. We thus propose to use ΣSFR and distance to the MS in conjunction to better identify the galaxy population undergoing a starbursting phase.

scholarly journals The Star Formation Reference Survey. IV. Stellar mass distribution of local star-forming galaxies

2021 ◽  
Author(s):  
P Bonfini ◽  
A Zezas ◽  
M L N Ashby ◽  
S P Willner ◽  
A Maragkoudakis ◽  
...  
Keyword(s):  
Star Formation ◽  
Mass Distribution ◽  
Star Formation Rate ◽  
Mass Density ◽  
Full Range ◽  
Formation Rate ◽  
Stellar Mass ◽  
Nearby Star ◽  
Star Forming ◽  
Mass Functions

Abstract We constrain the mass distribution in nearby, star-forming galaxies with the Star Formation Reference Survey (SFRS), a galaxy sample constructed to be representative of all known combinations of star formation rate (SFR), dust temperature, and specific star formation rate (sSFR) that exist in the Local Universe. An innovative two-dimensional bulge/disk decomposition of the 2MASS/Ks-band images of the SFRS galaxies yields global luminosity and stellar mass functions, along with separate mass functions for their bulges and disks. These accurate mass functions cover the full range from dwarf galaxies to large spirals, and are representative of star-forming galaxies selected based on their infra-red luminosity, unbiased by AGN content and environment. We measure an integrated luminosity density j = 1.72 ± 0.93 × 109 L⊙  h−1 Mpc−3 and a total stellar mass density ρM = 4.61 ± 2.40 × 108 M⊙  h−1 Mpc−3. While the stellar mass of the average star-forming galaxy is equally distributed between its sub-components, disks globally dominate the mass density budget by a ratio 4:1 with respect to bulges. In particular, our functions suggest that recent star formation happened primarily in massive systems, where they have yielded a disk stellar mass density larger than that of bulges by more than 1 dex. Our results constitute a reference benchmark for models addressing the assembly of stellar mass on the bulges and disks of local (z = 0) star-forming galaxies.

scholarly journals Effect of the environment on star formation activity and stellar mass for star-forming galaxies in the COSMOS field

2020 ◽  
Vol 499 (1) ◽  
pp. 948-956
Author(s):  
S M Randriamampandry ◽  
M Vaccari ◽  
K M Hess
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Cosmic Time ◽  
Stellar Mass ◽  
Star Forming ◽  
Galaxy Environment ◽  
Stellar Masses ◽  
The Relationship

ABSTRACT We investigate the relationship between the environment and the galaxy main sequence (the relationship between stellar mass and star formation rate), as well as the relationship between the environment and radio luminosity ($P_{\rm 1.4\, GHz}$), to shed new light on the effects of the environment on galaxies. We use the VLA-COSMOS 3-GHz catalogue, which consists of star-forming galaxies and quiescent galaxies (active galactic nuclei) in three different environments (field, filament, cluster) and for three different galaxy types (satellite, central, isolated). We perform for the first time a comparative analysis of the distribution of star-forming galaxies with respect to the main-sequence consensus region from the literature, taking into account galaxy environment and using radio observations at 0.1 ≤ z ≤ 1.2. Our results corroborate that the star formation rate is declining with cosmic time, which is consistent with the literature. We find that the slope of the main sequence for different z and M* bins is shallower than the main-sequence consensus, with a gradual evolution towards higher redshift bins, irrespective of environment. We see no trends for star formation rate in either environment or galaxy type, given the large errors. In addition, we note that the environment does not seem to be the cause of the flattening of the main sequence at high stellar masses for our sample.

scholarly journals xGASS: the role of bulges along and across the local star-forming main sequence

2020 ◽  
Vol 493 (4) ◽  
pp. 5596-5605 ◽  
Author(s):  
Robin H W Cook ◽  
Luca Cortese ◽  
Barbara Catinella ◽  
Aaron Robotham
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Formation Rate ◽  
Stellar Mass ◽  
Local Universe ◽  
Star Forming ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Stellar Masses

ABSTRACT We use our catalogue of structural decomposition measurements for the extended GALEX Arecibo SDSS Survey (xGASS) to study the role of bulges both along and across the galaxy star-forming main sequence (SFMS). We show that the slope in the sSFR–M⋆ relation flattens by ∼0.1 dex per decade in M⋆ when re-normalizing specifice star formation rate (sSFR) by disc stellar mass instead of total stellar mass. However, recasting the sSFR–M⋆ relation into the framework of only disc-specific quantities shows that a residual trend remains against disc stellar mass with equivalent slope and comparable scatter to that of the total galaxy relation. This suggests that the residual declining slope of the SFMS is intrinsic to the disc components of galaxies. We further investigate the distribution of bulge-to-total ratios (B/T) as a function of distance from the SFMS (ΔSFRMS). At all stellar masses, the average B/T of local galaxies decreases monotonically with increasing ΔSFRMS. Contrary to previous works, we find that the upper envelope of the SFMS is not dominated by objects with a significant bulge component. This rules out a scenario in which, in the local Universe, objects with increased star formation activity are simultaneously experiencing a significant bulge growth. We suggest that much of the discrepancies between different works studying the role of bulges originate from differences in the methodology of structurally decomposing galaxies.

scholarly journals SDSS-IV MaNGA: effects of morphology in the global and local star formation main sequences

2019 ◽  
Vol 488 (3) ◽  
pp. 3929-3948 ◽  
Author(s):  
M Cano-Díaz ◽  
V Ávila-Reese ◽  
S F Sánchez ◽  
H M Hernández-Toledo ◽  
A Rodríguez-Puebla ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Density ◽  
Main Sequence ◽  
Formation Rate ◽  
Stellar Mass ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Formation Activity ◽  
Global And Local ◽  
Universal Mechanism

ABSTRACT We study the global star formation rate (SFR) versus stellar mass (M*) correlation, and the spatially resolved SFR surface density (ΣSFR) versus stellar mass surface density (Σ*) correlation, in a sample of ∼2000 galaxies from the MaNGA MPL-5 survey. We classify galaxies and spatially resolved areas into star forming and retired according to their ionization processes. We confirm the existence of a star-forming main sequence (SFMS) for galaxies and spatially resolved areas, and show that they have the same nature, with the global as a consequence of the local one. The latter presents a bend below a limit Σ* value, ≈3 × 107 M$\odot$ kpc−2, which is not physical. Using only star-forming areas (SFAs) above this limit, a slope and a scatter of ≈1 and ≈0.27 dex are determined. The retired galaxies/areas strongly segregate from their respective SFMSs, by ∼−1.5 dex on average. We explore how the global/local SFMSs depend on galaxy morphology, finding that for star-forming galaxies and SFAs, there is a trend to lower values of star formation activity with earlier morphological types, which is more pronounced for the local SFMS. The morphology not only affects the global SFR due to the diminish of SFAs with earlier types, but also affects the local SF process. Our results suggest that the local SF at all radii is established by some universal mechanism partially modulated by morphology. Morphology seems to be connected to the slow aging and sharp decline of the SF process, and on its own it may depend on other properties as the environment.

scholarly journals The EDGE-CALIFA survey: Self-regulation of Star formation at kpc scales

2021 ◽  
Author(s):  
J K Barrera-Ballesteros ◽  
S F Sánchez ◽  
T Heckman ◽  
T Wong ◽  
A Bolatto ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Self Regulation ◽  
Stellar Mass ◽  
Good Representation ◽  
Star Forming ◽  
Star Forming Regions ◽  
Wide Range ◽  
Two Parameters ◽  
Stellar Masses

Abstract The processes that regulate star formation are essential to understand how galaxies evolve. We present the relation between star formation rate density, ΣSFR , and hydrostatic midplane pressure, Ph , for 4260 star-forming regions of kpc size located in 96 galaxies included in the EDGE-CALIFA survey covering a wide range of stellar masses and morphologies. We find that these two parameters are tightly correlated, showing a smaller scatter in comparison to other star-forming relations. A power-law, with a slightly sub-linear index, is a good representation of this relation. Its residuals show a significant anti-correlation with both stellar age and metallicity whereas the total stellar mass may also play a secondary role in shaping the ΣSFR - Ph relation. For actively star-forming regions we find that the effective feedback momentum per unit stellar mass (p*/m*), measured from the Ph/ΣSFR ratio increases with Ph. The median value of this ratio for all the sampled regions is larger than the expected momentum just from supernovae explosions. Morphology of the galaxies, including bars, does not seem to have a significant impact in the ΣSFR - Ph relation. Our analysis indicates that local ΣSFR self-regulation comes mainly from momentum injection to the interstellar medium from supernovae explosions. However, other mechanisms in disk galaxies may also play a significant role in shaping the ΣSFR at kpc scales. Our results also suggest that Ph is the main parameter that modulates star formation at kpc scales, rather than individual components of the baryonic mass.

scholarly journals Magnetic fields and massive star formation

2018 ◽  
Vol 14 (A30) ◽  
pp. 141-141
Author(s):  
Qizhou Zhang
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Massive Star ◽  
Dense Core ◽  
Continuum Emission ◽  
Massive Star Formation ◽  
Stellar Objects ◽  
Star Forming ◽  
Dense Cores ◽  
The Mean

AbstractMassive stars ( ${\rm{M}} > \,8{M_ \odot }$ ) often form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. The role of magnetic fields during the formation of massive dense cores is still not clear. The steady improvement in sensitivity of (sub)millimeter interferometers over the past decade enabled observations of dust polarization of large samples of massive star formation regions. We carried out a polarimetric survey with the Submillimeter Array of 14 massive star forming clumps in continuum emission at a wavelength of 0.89 mm. This unprecedentedly large sample of massive star forming regions observed by a submillimeter interferometer before the advent of ALMA revealed compelling evidence of strong magnetic influence on the gas dynamics from 1 pc to 0.1 pc scales. We found that the magnetic fields in dense cores tend to be either parallel or perpendicular to the mean magnetic fields in their parental molecular clumps. Furthermore, the main axis of protostellar outflows does not appear to be aligned with the mean magnetic fields in the dense core where outflows are launched. These findings suggest that from 1 pc to 0.1 pc scales, magnetic fields are dynamically important in the collapse of clumps and the formation of dense cores. From the dense core scale to the accretion disk scale of ∼102 au, however, gravity and angular momentum appear to be more dominant relative to the magnetic field.

scholarly journals The dependence of mass and environment on the secular processes of AGNs in terms of morphology, colour, and specific star-formation rate

2018 ◽  
Vol 620 ◽  
pp. A113 ◽  
Author(s):  
M. Argudo-Fernández ◽  
I. Lacerna ◽  
S. Duarte Puertas
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
High Mass ◽  
Late Type ◽  
Star Forming ◽  
Isolated Galaxies

Context. Galaxy mass and environment play a major role in the evolution of galaxies. In the transition from star-forming to quenched galaxies, active galactic nuclei (AGNs) also have a principal action therein. However, the connections between these three actors are still uncertain. Aims. In this work we investigate the effects of stellar mass and the large-scale structure (LSS) environment on the fraction of optical nuclear activity in a population of isolated galaxies, where AGN would not be triggered by recent galaxy interactions or mergers. Methods. As a continuation of a previous work, we focus on isolated galaxies to study the effect of stellar mass and the LSS in terms of morphology (early- and late-type), colour (red and blue), and specific star-formation rate (quenched and star-forming). To explore where AGN activity is affected by the LSS, we separate galaxies into two groups, of low- and high mass, respectively, and use the tidal strength parameter to quantify the effects. Results. We found that AGN is strongly affected by stellar mass in “active” galaxies (namely late-type, blue, and star-forming), but that mass has no influence on “quiescent” galaxies (namely early-type, red, and quenched), at least for masses down to 1010 M⊙. In relation to the LSS, we found an increase in the fraction of star-forming nuclei galaxies with denser LSS in low-mass star-forming and red isolated galaxies. Regarding AGN, we find a clear increase in the fraction of AGNs with denser environment in quenched and red isolated galaxies, independently of the stellar mass. Conclusions. Active galactic nuclei activity appears to be “mass triggered” in active isolated galaxies. This means that AGN activity is independent of the intrinsic properties of the galaxies, but is dependent on their stellar mass. On the other hand, AGN activity appears to be “environment triggered” in quiescent isolated galaxies, where the fraction of AGNs as a function of specific star formation rate and colour increases from void regions to denser LSS, independently of stellar mass.

scholarly journals PHIBSS2: survey design and z = 0.5 – 0.8 results

2019 ◽  
Vol 622 ◽  
pp. A105 ◽  
Author(s):  
J. Freundlich ◽  
F. Combes ◽  
L. J. Tacconi ◽  
R. Genzel ◽  
S. Garcia-Burillo ◽  
...  
Keyword(s):  
Star Formation ◽  
Survey Design ◽  
Formation Rate ◽  
Sample Selection ◽  
Stellar Mass ◽  
Gas Content ◽  
Molecular Gas ◽  
Star Forming ◽  
Gas Measurements ◽  
Deep Fields

Following the success of the Plateau de Bure high-z Blue Sequence Survey (PHIBSS), we present the PHIBSS2 legacy program, a survey of the molecular gas properties of star-forming galaxies on and around the star-formation main sequence (MS) at different redshifts using IRAM’s NOrthern Extended Millimeter Array (NOEMA). This survey significantly extends the existing sample of star-forming galaxies with CO molecular gas measurements, probing the peak epoch of star formation (z = 1 − 1.6) as well as its building-up (z = 2 − 3) and winding-down (z = 0.5 − 0.8) phases. The targets are drawn from the well-studied GOODS, COSMOS, and AEGIS cosmological deep fields and uniformly sample the MS in the stellar mass (M⋆) – star formation rate (SFR) plane with log(M⋆/M⊙) = 10 − 11.8 and SFR = 3.5 − 500 M⊙ yr−1 without morphological selection, thus providing a statistically meaningful census of star-forming galaxies at different epochs. We describe the survey strategy and sample selection before focusing on the results obtained at redshift z = 0.5 − 0.8, where we report 60 CO(2-1) detections out of 61 targets. We determine molecular gas masses between 2 × 109 and 5 × 1010 M⊙ and separately obtain disc sizes and bulge-to-total (B/T) luminosity ratios from HST I-band images. The median molecular gas-to-stellar mass ratio μgas∼ = 0.28 ± 0.04, gas fraction fgas∼ = 0.22 ± 0.02, and depletion time $ \widetilde{t_{\mathrm{depl}}} = 0.84 \pm 0.07\,\mathrm{Gyr} $ as well as their dependence with stellar mass and offset from the MS follow published scaling relations for a much larger sample of galaxies spanning a significantly wider range of redshifts, the cosmic evolution of the SFR being mainly driven by that of the molecular gas fraction. The galaxy-averaged molecular Kennicutt–Schmidt (KS) relation between molecular gas and SFR surface densities is strikingly linear, pointing towards similar star formation timescales within galaxies at any given epoch. In terms of morphology, the molecular gas content, the SFR, the disc stellar mass, and the disc molecular gas fraction do not seem to correlate with B/T and the stellar surface density, which suggests an ongoing supply of fresh molecular gas to compensate for the build-up of the bulge. Our measurements do not yield any significant variation of the depletion time with B/T and hence no strong evidence for morphological quenching within the scatter of the MS.

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

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.

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