scholarly journals Quenching star formation at intermediate redshifts: downsizing of the mass flux density in the green valley

2012 ◽  
Vol 8 (S295) ◽  
pp. 163-166
Author(s):  
Thiago S. Gonçalves ◽  
D. Christopher Martin ◽  
Karín Menéndez-Delmestre ◽  
Ted K. Wyder ◽  
Anton Koekemoer
Keyword(s):  
Star Formation ◽  
Flux Density ◽  
Mass Flux ◽  
High Redshift ◽  
Massive Galaxies ◽  
Star Forming ◽  
Star Formation Histories ◽  
Intermediate Redshifts ◽  
The Universe ◽  
Red Sequence

AbstractThe bimodality in galaxy properties has been observed at low and high redshift, with a clear distinction between star-forming galaxies in the blue cloud and passively evolving objects in the red sequence; the absence of galaxies with intermediate properties indicates that the quenching of star formation and subsequent transition between populations must happen rapidly. In this work, we present a study of over 100 transiting galaxies in the so-called “green valley” at intermediate redshifts (z ~ 0.8). By using very deep spectroscopy with the DEIMOS instrument at the Keck telescope, we are able to infer the star formation histories of these objects and measure the stellar mass flux density transiting from the blue cloud to the red sequence when the Universe was half its current age. Our results indicate that the process happened more rapidly, affecting more massive galaxies in the past, suggesting a top-down scenario whereby the massive end of the red sequence assembles first. This represents another aspect of downsizing, with the mass flux density moving towards smaller galaxies in recent times.

scholarly journals Quenching Star Formation in the Green Valley: The Mass Flux at Intermediate Redshifts

2009 ◽  
Vol 5 (S262) ◽  
pp. 261-264
Author(s):  
Thiago S. Gonçalves ◽  
D. Christopher Martin
Keyword(s):  
Star Formation ◽  
Flux Density ◽  
Mass Flux ◽  
Mass Loss Rate ◽  
Star Formation Histories ◽  
Intermediate Redshift ◽  
Intermediate Redshifts ◽  
Two Populations ◽  
Lower Redshift ◽  
Red Sequence

AbstractWe have obtained several hundred very deep spectra with DEIMOS/Keck in order to estimate the galactic mass flux density at intermediate redshifts (0.6 < z < 0.9) from the "blue cloud" to the red sequence across the so-called “green valley”, the intermediate region in the color-magnitude plot between those two populations. We use spectral indices (specifically Dn(4000) and Hδ, A) to determine star formation histories. Together with an independent measurement of number density of galaxies in each bin of the color-magnitude plot, one can infer the rate at which galaxies from a given sample are transiting through that bin. Measuring this value for all magnitude values, studies at lower redshift determined that the mass flux density in the green valley is comparable to both the mass build-up rate of the red sequence and the mass loss rate from the blue cloud. We show preliminary results for our intermediate redshift sample.

Panchromatic study of the first galaxies in cosmological simulations

2019 ◽  
Vol 15 (S341) ◽  
pp. 240-244
Author(s):  
Hidenobu Yajima ◽  
Shohei Arata ◽  
Makito Abe ◽  
Kentaro Nagamine
Keyword(s):  
Star Formation ◽  
Initial Conditions ◽  
High Redshift ◽  
Radiative Properties ◽  
Massive Galaxies ◽  
Star Forming ◽  
Lyman Alpha ◽  
Radiation Properties ◽  
Multi Wavelength ◽  
First Galaxies

AbstractRecent discoveries of high-redshift galaxies have revealed the diversity of their physical properties, from normal star-forming galaxies to starburst galaxies. To understand the properties of these observed galaxies, it is crucial to understand the star formation (SF) history, and the radiation properties associated with the SF activity. Here we present the results of cosmological hydrodynamic simulations with zoom-in initial conditions, and show the formation of the first galaxies and their evolution towards observable galaxies at z = 6. In addition, we show their multi-wavelength radiative properties. We find that star formation occurs intermittently due to supernova (SN) feedback at z > 10, and their radiation properties rapidly change with time. We suggest that the first galaxies are bright at UV wavelengths just after the starburst phase, and become extended Lyman-alpha sources. We also show that massive galaxies cause dusty starburst and become bright at infrared wavelengths.

scholarly journals Modelling Stellar Populations at High Redshift

2010 ◽  
Vol 6 (S277) ◽  
pp. 158-165
Author(s):  
Claudia Maraston
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Stellar Populations ◽  
Star Formation History ◽  
Population Modelling ◽  
Massive Galaxies ◽  
Star Forming ◽  
Formation History ◽  
Derived Properties ◽  
Stellar Masses

AbstractStellar populations carry information about the formation of galaxies and their evolution up to the present epoch. A wealth of observational data are available nowadays, which are analysed with stellar population models in order to obtain key properties such as ages, star formation histories, stellar masses. Differences in the models and/or in the assumptions regarding the star formation history affect the derived properties as much as differences in the data. I shall review the interpretation of high-redshift galaxy data from a model perspective. While data quality dominates galaxy analysis at the highest possible redshifts (z > 5), population modelling effects play the major part at lower redshifts. In particular, I discuss the cases of both star-forming galaxies at the peak of the cosmic star formation history as well as passive galaxies at redshift below 1 that are often used as cosmological probes. Remarks on the bridge between low and high-z massive galaxies conclude the contribution.

scholarly journals Red and dead CANDELS: massive passive galaxies at the dawn of the Universe

2019 ◽  
Vol 490 (3) ◽  
pp. 3309-3328 ◽  
Author(s):  
E Merlin ◽  
F Fortuni ◽  
M Torelli ◽  
P Santini ◽  
M Castellano ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Formation Rate ◽  
Probabilistic Approach ◽  
Big Bang ◽  
Spectral Lines ◽  
Massive Galaxies ◽  
Star Formation Activity ◽  
Star Formation Histories ◽  
The Big Bang

ABSTRACT We search the five CANDELS fields (COSMOS, EGS, GOODS-North, GOODS-South, and UDS) for passively evolving a.k.a. ‘red and dead’ massive galaxies in the first 2 Gyr after the big bang, integrating and updating the work on GOODS-South presented in a previous paper. We perform SED-fitting on photometric data, with top-hat star-formation histories to model an early and abrupt quenching, and using a probabilistic approach to select only robust candidates. Using libraries without (with) spectral lines emission, starting from a total of more than 20 000 z > 3 sources we end up with 102 (40) candidates, including one at z = 6.7. This implies a minimal number density of 1.73 ± 0.17 × 10−5 (6.69 ± 1.08 × 10−6) Mpc−3 for 3 < z < 5; applying a correction factor to account for incompleteness yields 2.30 ± 0.20 × 10−5. We compare these values with those from five recent hydrodynamical cosmological simulations, finding a reasonable agreement at z < 4; tensions arise at earlier epochs. Finally, we use the star-formation histories from the best-fitting models to estimate the contribution of the high-redshift passive galaxies to the global star formation rate density during their phase of activity, finding that they account for ∼5–10 per cent of the total star formation at 3 < z < 8, despite being only $\sim 0.5{{\ \rm per\ cent}}$ of the total in number. The resulting picture is that early and strong star formation activity, building massive galaxies on short time-scales and followed by a quick and abrupt quenching, is a rare but crucial phenomenon in the early Universe: the evolution of the cosmos must be heavily influenced by the short but powerful activity of these pristine monsters.

scholarly journals Rejuvenated galaxies with very old bulges at the origin of the bending of the main sequence and of the ‘green valley’

2019 ◽  
Vol 489 (1) ◽  
pp. 1265-1290 ◽  
Author(s):  
Chiara Mancini ◽  
Emanuele Daddi ◽  
Stéphanie Juneau ◽  
Alvio Renzini ◽  
Giulia Rodighiero ◽  
...  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Formation Rate ◽  
Very Old ◽  
Massive Galaxies ◽  
Star Forming ◽  
Late Event ◽  
Age Of The Universe ◽  
Stellar Masses ◽  
Star Formation Histories

ABSTRACT We investigate the nature of star-forming galaxies with reduced specific star formation rate (sSFR) and high stellar masses, those ‘green valley’ objects that seemingly cause a reported bending, or flattening, of the star-forming main sequence. The fact that such objects host large bulges recently led some to suggest that the internal formation of bulges was a late event that induced the sSFRs of massive galaxies to drop in a slow downfall, and thus the main sequence to bend. We have studied in detail a sample of 10 galaxies at 0.45 &lt; z &lt; 1 with secure SFR from Herschel, deep Keck optical spectroscopy, and HST imaging from CANDELS allowing us to perform multiwavelength bulge to disc decomposition, and to derive star formation histories for the separated bulge and disc components. We find that the bulges hosted in these systems below main sequence are virtually all maximally old, with ages approaching the age of the Universe at the time of observation, while discs are young (〈 T50〉 ∼ 1.5 Gyr). We conclude that, at least based on our sample, the bending of the main sequence is, for a major part, due to rejuvenation, and we disfavour mechanisms that postulate the internal formation of bulges at late times. The very old stellar ages of our bulges suggest a number density of early-type galaxies at z = 1–3 higher than actually observed. If confirmed, this might represent one of the first direct validations of hierarchical assembly of bulges at high redshifts.

scholarly journals GOODS-Herschel: Dust attenuation up to z∼4

2012 ◽  
Vol 8 (S292) ◽  
pp. 289-289 ◽  
Author(s):  
M. Pannella ◽  
D. Elbaz ◽  
E. Daddi
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Line Emission ◽  
Stellar Mass ◽  
Massive Galaxies ◽  
Star Forming ◽  
Main Driver ◽  
Galaxy Sample ◽  
Stellar Masses ◽  
Dust Attenuation

AbstractWe quantitatively explore in a unbiased way the evolution of dust attenuation up to z ≈ 4 as a function of galaxy properties. We have used one of the deepest datasets available at present, in the GOODS-N field, to select a star forming galaxy sample and robustly measure galaxy redshifts, star formation rates, stellar masses and UV restframe properties. Our main results can be summarized as follows: i) we confirm that galaxy stellar mass is a main driver of UV dust attenuation in star forming galaxies: more massive galaxies are more dust attenuated than less massive ones; ii) strikingly, we find that the correlation does not evolve with redshift: the amount of dust attenuation is the same at all cosmic epochs for a fixed stellar mass; iii) this finding explains why and how the SFR–AUV relation evolves with redshift: the same amount of star formation is less attenuated at higher redshift because it is hosted in less massive galaxies; iv) combining our finding with results from line emission surveys, we confirm that line reddening is larger than continuum reddening, at least up to z ≈ 1.5; v) given the redshift evolution of the mass-metallicity relation, we predict that star forming galaxies at a fixed metal content are more attenuated at high redshift. Finally, we explored the correlation between UV dust attenuation and the spectral slope: vi) the correlation is evolving with redshift with star forming galaxies at lower redshift having redder spectra than higher redshift ones for the same amount of dust attenuation.

scholarly journals Galaxies in most dense environments at z ~ 1.4

2012 ◽  
Vol 10 (H16) ◽  
pp. 377-377
Author(s):  
V. Strazzullo
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Cosmic Time ◽  
Cluster Center ◽  
Final Conclusion ◽  
Early Type ◽  
Massive Galaxies ◽  
Star Forming ◽  
Cluster Cores ◽  
Red Sequence

AbstractThe X-ray luminous system XMMU J2235-2557 at z~1.4 is among the most massive of the very distant galaxy clusters, and remains a unique laboratory to observe environment-biased galaxy evolution already 9 Gyr ago (Lidman et al.2008, Rosati et al.2009, Strazzullo et al.2010). At a cosmic time when cluster cores start showing evidence of a still active galaxy population, star-forming (M>1010M⊙) galaxies in XMMU J2235-2557 are typically located beyond ~250kpc from the cluster center, with the cluster core already effectively quenched and dominated by massive galaxies on a tight red sequence, showing early-type spectral features and bulge-dominated morphologies. While masses and stellar populations of these red-sequence galaxies suggest that they have largely completed their formation, their size is found to be typically smaller that similarly massive early-type galaxies in the local Universe, in agreement with many high-redshift studies. This would leave room for later evolution, likely through non-secular processes, changing their structure to match their local counterparts. On the other hand, uncertainties and biases in the determination of masses and sizes, as well as in the local mass-size relation, and the possible effect of progenitor bias, still hamper a final conclusion on the actual relevance of size evolution for early-type galaxies in this dense high-redshift environment.

scholarly journals Luminosities, Masses and Star Formation Rates of Galaxies at High Redshift

2011 ◽  
Vol 7 (S279) ◽  
pp. 224-231
Author(s):  
Andrew J. Bunker
Keyword(s):  
Star Formation ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Formation Rate ◽  
Large Contribution ◽  
Star Forming ◽  
Dust Extinction ◽  
Lyman Break Galaxies ◽  
Current Detection ◽  
The Universe

AbstractThere has been great progress in recent years in discovering star forming galaxies at high redshifts (z > 5), close to the epoch of reionization of the intergalactic medium (IGM). The WFC3 and ACS cameras on the Hubble Space Telescope have enabled Lyman break galaxies to be robustly identified, but the UV luminosity function and star formation rate density of this population at z = 6 − 8 seems to be much lower than at z = 2 − 4. High escape fractions and a large contribution from faint galaxies below our current detection limits would be required for star-forming galaxies to reionize the Universe. We have also found that these galaxies have blue rest-frame UV colours, which might indicate lower dust extinction at z > 5. There has been some spectroscopic confirmation of these Lyman break galaxies through Lyman-α emission, but the fraction of galaxies where we see this line drops at z > 7, perhaps due to the onset of the Gunn-Peterson effect (where the IGM is opaque to Lyman-α).

High-redshift starbursts as progenitors of massive galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 22-26
Author(s):  
Carlos Gómez-Guijarro
Keyword(s):  
Star Formation ◽  
Compact Star ◽  
High Redshift ◽  
Stellar Mass ◽  
Starburst Galaxies ◽  
The Other ◽  
Massive Galaxies ◽  
Star Forming ◽  
Spatially Resolved ◽  
Minor Mergers

AbstractStarbursting dust-rich galaxies are capable of assembling large amounts of stellar mass very quickly. They have been proposed as progenitors of the population of compact massive quiescent galaxies at z ˜ 2. To test this connection, we present a detailed spatially-resolved study of the stars, dust, and stellar mass in a sample of six submillimeter-bright starburst galaxies at z ˜ 4.5. We found that the systems are undergoing minor mergers and the bulk star formation is located in extremely compact regions. On the other hand, optically-compact star forming galaxies have also been proposed as immediate progenitors of compact massive quiescent galaxies. Were they formed in slow secular processes or in rapid merger-driven starbursts? We explored the location of galaxies with respect to star-forming and structural relations and study the burstiness of star formation. Our results suggest that compact star-forming galaxies could be starbursts winding down and eventually becoming quiescent.

scholarly journals The star formation histories of the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 138-138
Author(s):  
H. R. Butcher
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Local Group ◽  
High Redshift ◽  
Magellanic Clouds ◽  
Empirical Methods ◽  
Star Forming ◽  
Two Systems ◽  
The Galaxy ◽  
Star Formation Histories

Existing observations of the Magellanic Clouds suggest substantially different star-forming histories for the two systems. The reliability of this conclusion is discussed in the context of the uncertainties and age resolutions of various empirical methods of studying galaxy evolution. An attempt is also made to relate likely evolutionary scenarios for the Clouds to the histories of other Local Group systems, to the evolution seen in galaxies at high redshift, and to possible histories determined by interaction with the Galaxy.

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