Emission line galaxies are the most easily detected and studied objects in the high redshift Universe. They are being used to trace the evolution of the critical observables of the Universe such as star formation rate densities, starburst properties, and abundances. The GTC will b e a very powerful tool for studying the evolution of emission line galaxy populations at different redshifts. Large surveys, such as OTELO, carried out with OSIRIS and extended by follow-up spectroscopic studies in the near infrared using EMIR will enable the GTC to make a major impact in extragalactic astronomy

Gallego Maestro, Jesús

Revista Mexicana de Astronomía y Astrofísica

English

© The SAO/NASA 2003. Meeting on Science with the GTC (1st. 2002. Granada/Spain). My collaborators on the papers and projects relevant to this contribution were E. Alfaro, M. Balcells, J. Cepa, J. González, I. González-Serrano, R. Guzmán, S. Pascual, R. Pelló, M. Sánchez-Portal, and J. Zamorano. This work was supported in part by the Spanish Plan Nacional de Astronomía y Astrofísica under grant AYA2000-1790.Emission line galaxies are the most easily detected and studied objects in the high redshift Universe. They are being used to trace the evolution of the critical observables of the Universe such as star formation rate densities, starburst properties, and abundances. The GTC will b e a very powerful tool for studying the evolution of emission line galaxy populations at different redshifts. Large surveys, such as OTELO, carried out with OSIRIS and extended by follow-up spectroscopic studies in the near infrared using EMIR will enable the GTC to make a major impact in extragalactic astronomy.Las galaxias con líneas de emisión son los objetos más fáciles de detectar y estudiar en el Universo a alto desplazamiento al rojo. Están siendo usadas para trazar la evolución de observables críticos del Universo, tales como densidades de tasa de formación estelar, propiedades de los procesos de formación estelar y abundancias. GTC constituirá una herramienta muy potente para el estudio de la evolución de las poblaciones de galaxias con líneas de emisión a diferentes desplazamientos al rojo. Grandes exploraciones como OTELO, llevada a cabo con OSIRIS y extendida mediante espectroscopía infrarroja con EMIR, permitirán a GTC contribuir con un gran impacto en el campo de la Astronomía Extragaláctica.Plan Nacional de Astronomía y Astrofísica (España)Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEpu

Docta Complutense

Science with the GTC 10-m Telescope (Granada, España, 5-8 febrero 2002)Editors: José Miguel Rodríguez Espinosa, Francisco Garzón López & Verónica Melo MartínRevMexAA (Serie de Conferencias), 16, 221–224 (2003)GALAXY EVOLUTION STUDIES OBSERVINGEMISSION LINE GALAXIES WITH THE GTCJ. GallegoUniversidad Complutense de Madrid, Madrid, SpainRESUMENLas galaxias con ĺıneas de emisión son los objetos más fáciles de detectar y estudiar en el Universo a altodesplazamieno al rojo. Están siendo usadas para trazar la evolución de observables cŕıticos del Universo, talescomo densidades de tasa de formación estelar, propiedades de los procesos de formación estelar y abundancias.GTC constituirá una herramienta muy potente para el estudio de la evolución de las poblaciones de galaxiascon ĺıneas de emisión a diferentes desplazamientos al rojo. Grandes exploraciones como OTELO, llevada acabo con OSIRIS y extendida mediante espectroscoṕıa infrarroja con EMIR, permitirán a GTC contribuir conun gran impacto en el campo de la Astronomı́a Extragaláctica.ABSTRACTEmission line galaxies are the most easily detected and studied objects in the high redshift Universe. Theyare being used to trace the evolution of the critical observables of the Universe such as star formation ratedensities, starburst properties, and abundances. The GTC will be a very powerful tool for studying theevolution of emission line galaxy populations at different redshifts. Large surveys, such as OTELO, carried outwith OSIRIS and extended by follow-up spectroscopic studies in the near infrared using EMIR will enable theGTC to make a major impact in extragalactic astronomy.Key Words: GALAXIES : EVOLUTION — GALAXIES1. EMISSION-LINE GALAXY SURVEYS ANDGALAXY EVOLUTIONSeveral surveys of emission line galaxies (here-after ELGs) have been carried out in recent decades,covering large portions of the sky (see Zamoranoet al. 1994 for a review). Most of these surveyshave targeted the blue part of the optical spectrumfor the detection of strong emission lines, such as[O III] λ5007. A small fraction of these projectsfocused on the red part of the spectrum and usedthe presence of the Balmer Hα and the neighboring[N II] λ6548,6584 emission lines. All these surveyswere excellent sources for catalogs of extreme starforming galaxies, active galactic nuclei, and bizarreobjects, and one of their main goals was to detectlow luminosity blue compact galaxies (BCGs) withlow metallicities. Surveys carried out in the red wereconsidered to be “contaminated” because of theirability to detect all kinds of star forming galaxies,but this property turned out to be a very power-ful tool as the interest of researchers shifted fromextreme objects to the average properties of galaxypopulations.The arrival of the Hubble Space Telescope (HST )and the new generation of 8 m class telescopes deter-mined a whole series of studies about the nature ofthe galaxy populations of the Universe at differentredshifts and their corresponding look-back times.Because emission lines are easier to observe, faintgalaxy samples are mostly populated by ELGs. Theneed for well-studied local reference samples for sim-ilar galaxy samples at all redshifts has triggered re-newed interest in classic surveys such as the Universi-dad Complutense de Madrid (UCM) survey for localstar forming galaxies (Zamorano et al. 1994, 1996).It is possible now to sketch the overall evolution ofobservational quantities as a function of look-backtime, as illustrated by the pioneering work of Madauet al. (1996) on the evolution of the current star for-mation rate (SFR) of the Universe. These authorscombined 1500 Å UV luminosities of the high red-shift galaxies in the Hubble Deep Field (Williams etal. 1996), with 2800 Å UV luminosities of the inter-mediate redshift galaxies of the Canada–France Red-shift Survey (CFRS, Lilly et al. 1996) and the SFRdensity of the local Universe, which was measuredusing Hα as a tracer by Gallego et al. (1995).In recent years, 8 m class telescopes have gath-ered large samples of galaxies at different redshifts.The overall evolution of properties of the Universe,221Science with the GTC 10-m Telescope (Granada, España, 5-8 febrero 2002)Editors: José Miguel Rodríguez Espinosa, Francisco Garzón López & Verónica Melo Martín222 GALLEGOFig. 1. Left: The evolution of the [O II] λ3727 luminosity density of the Universe up to z ∼ 1.4 (Gallego et al. 2002). Theobserved and extinction-corrected values for the UCM sample are represented as filled and open triangles, respectively.Filled circles correspond to Hogg et al. (1998), filled stars are for the Hammer et al. (1997) values, and the filled andopen squares are for the observed and extinction-corrected Sullivan et al. (2000) values. Right: Comparison of theobserved Hα luminosities measured by the different surveys of Hα emission line galaxies at various redshifts (See textfor details). The cosmology assumed was H0 = 50 km s−1 Mpc−1, Ωm = 1.0, and ΩΛ = 0. Symbols are the same as forFigure 2.such as the luminosity densities in given emissionlines, are now being obtained (see Figure 1). Theseprojects will be also be able to tackle the generalevolution of galaxies, large scale structure, and theanalysis of new kinds of galaxies. However, becauseof their simple photometric selection technique (allobjects brighter than a given apparent magnitude ora combination of two filters), they will leave furtherwork to be done in specific fields of research.2. ELG STUDIES WITH OSIRISIt is clear from Figure 1 that evolution since z ∼ 1has been confirmed in the overall properties of starforming galaxy populations. However, these resultscannot go much further because they are obtainedfrom poor samples, given that the number of ob-jects per redshift bin is small (sometimes only a fewgalaxies), and that only bright objects are being se-lected by current techniques. What remains to beascertained are the changes in conditions and galaxyproperties that motivated this evolution.The tunable filters to be used with OSIRIS on theGTC (see Cepa et al., this volume, p. 13) will pro-vide to the GTC community with a unique tool forselecting samples at a well-defined redshift range bytheir luminosities in a specific emission line. OTELOis a proposed GTC key project (see Cepa et al., thisvolume, p. 66) whose main goal will be to detect andstudy representative and complete samples of galax-ies necessary for the study of the overall propertiesand physical conditions of emission galaxy popula-tions at specific look-back times.Table 1 summarizes the main characteristics ofOTELO. Tunable filters will be used to scan the skyin three well defined wavelength windows that corre-spond with Hα redshifted to z = 0.09, 0.24, and 0.40.These windows have been selected for their low skyemission. Each window will be covered for a differentsky area and a different flux limit to ensure a mini-mum of Hα emitters close to 500. As a natural result,[O III] λ 5007, Hβ, and [O II] λ3727 emitters will alsobe detected, providing a total of nine redshift rangesfrom z = 0.09 to z = 1.46 scanned for ELGs. Theexpected number of ELGs per OSIRIS field has beenestimated assuming an evolution coherent with thebehavior observed in Figure 1 (Pascual et al. 2001).As a general deep survey, OTELO will also be ofgreat interest in the fields of blue compact galaxies,AGN, quasars, and Galactic astronomy.The key science case for the OTELO project willbe the evolution of the physical properties of the cur-rent star forming galaxy population at different red-shifts as traced by their Hα luminosities and equiva-lent widths. These parameters, when combined withmultiband photometric data, allow the estimationof burst age, strength, and metallicity (see Gil dePaz et al. 2000). If additional information is addedin the K band, it is also possible to estimate themass-to-luminosity ratio and the total stellar massof the system. The complementing photometry willbe also used to confirm the nature of the emissionline detected using the photometric redshift tech-nique. The OTELO survey will be carried out withsufficient spectral resolution to resolve Hα from theScience with the GTC 10-m Telescope (Granada, España, 5-8 febrero 2002)Editors: José Miguel Rodríguez Espinosa, Francisco Garzón López & Verónica Melo MartínEMISSION LINE GALAXY STUDIES WITH GTC 223TABLE 1OTELO OBSERVING WINDOWSWin. λ range Flux limit z for Hα z for z for Higher z Total Hα Total(Å) erg cm−2 s−1 Hα ELGsa [O III] λ5007 [O II] λ3727 ELGs b ELGs ELGsW1 7075-7250 2 × 10−16 0.09 0.5 0.43 0.92 1.5 500 2000W2 8072-8247 3 × 10−17 0.24 8.8 0.62 1.18 51.7 502 3449W3 9060-9300 1 × 10−17 0.40 50.7 0.84 1.46 283.5 507 3342aExpected number per OSIRIS field assuming an evolution as Pascual et al. (2001).bExpected number of Hα+[O III] λ5007 + [O II] λ3727 emitters assuming the same evolution.Fig. 2. Comparison of the Hα fluxes measured by the different surveys of Hα ELGs at various redshifts (See text fordetails). In the upper part of the figure, the corresponding redshifts to observe Hα in the NIR J , H, and K bands havealso been represented.adjacent [ N II]λ6548,6584 emission lines. The Hαover [N II] λ6584 ratio is also a good indicator of thenitrogen gas metallicity and it will be used to traceits evolution with redshift and better estimate theSFR from the Hα luminosity (Weilbacher & Fritze-v.Alvensleben 2001).In Figure 2 are plotted the Hα fluxes that havebeen measured by the various surveys of Hα ELGs atdifferent redshifts. The full curve is the expected fluxfor an L∗Hαat z = 0 with log(LHα) = 42.15 erg s−1(Gallego et al. 1995), assuming an extinction cor-rection of AHα = 1 mag and a cosmology of H0 =50 km s−1 Mpc−1, Ωm = 1.0, and ΩΛ = 0. Thedashed and dot–dashed curves are for 10×L∗Hαand0.1×L∗Hα. The local Universe is represented by theUCM survey (Gallego et al. 1997). The Universe atz = 0.24 and z = 0.40 are the narrow band filter sur-veys carried out by Pascual et al. (2001) and Jones &Bland-Hawthorn (2001). The other objects at higherredshift are from near infrared spectroscopy obtainedwith 8 m telescopes (Tresse et al. 2002; Glazebrooket al. 1999) and serendipitous discoveries in slitlessspectroscopy observations with NICMOS (McCarthyet al. 2001; Hopkins et al. 2001). At z = 2.2, thereScience with the GTC 10-m Telescope (Granada, España, 5-8 febrero 2002)Editors: José Miguel Rodríguez Espinosa, Francisco Garzón López & Verónica Melo Martín224 GALLEGOare a few objects available that have been detectedby Moorwood et al. (2001) using a narrow band filterin K. Finally, the z ∼ 3 values are rough estimatesfrom the observed Hβ fluxes published by Pettini etal. (2001).It is clear from Figures 1 and 2 that we only knowabout the most luminous fraction of the star forminggalaxies at high redshift. The hatched rectangles atz = 0.09, 0.24, and 0.4 in Figure 2 correspond tothe three planned OTELO redshift ranges and fluxlimits. The values selected (see Table 1) are thosecorresponding to an Hα emission line luminosity of∼1040 erg s−1 at that redshift. This luminosity isfainter than 0.1×L∗Hαin the local Universe and willallow us to cover a wide range in luminosities, in-cluding the expected but still unknown populationof low luminosity star forming galaxies that are sup-posed to play a key role in the overall evolution ofthe SFR density of the Universe. The number den-sity and physical properties of this kind of object willprovide galaxy evolution models with critical con-tour conditions. OSIRIS could be also used to ob-tain optical spectroscopy for more detailed studies ofspecific subsamples of objects.3. ELGS STUDIES IN THE NEAR-INFRAREDThe GTC will be an even more powerful toolfor studying galaxy evolution when the imagerand multiobject spectrograph in the near infrared(EMIR) is commissioned. An obvious extensionof OTELO with EMIR will be the follow-up nearinfrared spectroscopy of those [O II] λ3727 and[O III] λ5007 emitters selected from the tunablefilter images. This work will extend up to z = 1.46the same analysis carried out for the Hα emittersat z = 0.09, 0.24, and 0.40. EMIR could alsoprovide deep imaging in the NIR bands. An-other extension of the OTELO project will be touse OSIRIS equipped with an eventual tunablefilter in the NIR, or simulate its functionalityusing narrow band filters with EMIR in theimaging mode. A new IR–OTELO would allow usJ. Gallego: Departamento de Astrof́ısica y Ciencias de la Atmósfera, Universidad Complutense de Madrid,E-28040 Madrid, Spain (jgm@astrax.fis.ucm.es).to build new analogous samples of Hα ELGs fromz ∼ 0.8 up to z ∼ 2.5.Only with well focused science case studies willthe GTC attain long-lasting impact in key fields ofastronomical research.My collaborators on the papers and projects rele-vant to this contribution were E. Alfaro, M. Balcells,J. Cepa, J. González, I. González-Serrano, R. Guz-mán, S. Pascual, R. Pelló, M. Sánchez-Portal, andJ. Zamorano. This work was supported in part bythe Spanish Plan Nacional de Astronomı́a y Astro-f́ısica under grant AYA2000-1790.REFERENCESGallego, J., Zamorano, J., Aragón-Salamanca, A., &Rego, M. 1995, ApJ, 455, L1Gallego, J., Zamorano, J., Rego, M., & Vitores, A. G.1997, ApJ, 475, 502Gallego, J., et al. 2002, ApJL, in pressGil de Paz, A., et al. 2000, MNRAS, 316, 357Glazebrook, K., et al. 1999, MNRAS, 306, 843Hogg, D. W., Cohen, J. G., Blandford, R., & Pahre,M. A. 1998, ApJ, 504, 622Hammer, F., et al. 1997, ApJ, 481, 49Hopkins, A., Connolly, A., & Szalay, A. 2000, AJ, 120,2843Jones, D. H., & Bland-Hawthorn, J. 2001, ApJ, 550, 593Lilly, S., Le Févre, O., Hammer, F., & Crampton, D.1996, ApJ, 460, L1Madau, P., et al. 1996, MNRAS, 283, 1388McCarthy, P. J., et al. 1999, ApJ, 520, 548Moorwood, A. F. M., et al. 2001, A&A, 362, 9Pascual, S., Gallego, J., Aragón-Salamanca, A., &Zamorano, J. A&A, 379, 798Pettini, M., et al. 2001, ApJ, 554, 2Sullivan, M., et al. 2000, MNRAS, 312, 442Tresse, L., et al. 2002, MNRAS (astro-ph/0111390)Weilbacher, P, Fritze-v.Alvesleben, U. 2001, A&A, 373,L9Williams, R. E., et al. 1996, AJ, 112, 1335Zamorano, J., et al. 1994, ApJS, 95, 387Zamorano, J., et al. 1996, ApJS, 105, 343

Galaxy evolution studies observing emission line galaxies with the GTC

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Galaxy evolution studies observing emission line galaxies with the GTC

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